Systems and methods for aperiodic measurement reference signal transmission in multiple antenna systems

ABSTRACT

Systems and methods are disclosed for determining a first downlink control indicator (DCI) and a second DCI, determining a set of active aperiodic channel state information reference signals (A-CSI-RSs) based on the first DCI, and determining a subset of the set of active A-CSI-RSs based on the second DCI. A WTRU may perform resource element (RE) muting based on a set of active A-CSI-RSs. A WTRU may perform channel state information (CSI) measurement based on a subset of a set of active A-CSI-RSs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage entry under 35 U.S.C. § 371 ofPatent Cooperation Treaty Application PCT/US2017/046224, filed Aug. 10,2017, entitled “SYSTEMS AND METHODS FOR APERIODIC MEASUREMENT REFERENCESIGNAL TRANSMISSION IN MULTIPLE ANTENNA SYSTEMS,” which claims priorityto U.S. Provisional Patent Application Ser. No. 62/373,248, filed Aug.10, 2016, entitled “SYSTEMS AND METHODS FOR APERIODIC MEASUREMENTREFERENCE SIGNAL TRANSMISSION IN MULTIPLE ANTENNA SYSTEMS,” which isincorporated herein by reference in its entirety.

BACKGROUND

A channel state information reference signal (CSI-RS) may be used formeasurement purposes in Long-Term Evolution (LTE) wirelesscommunications systems. One or more patterns of CSI-RSs may be afunction of a number of antenna ports that may be in use by a devicegenerating such patterns. Such patterns may be provided in atransmission subframe.

SUMMARY

The Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key featuresand/or essential features of the claimed subject matter, nor is itintended to be used to limit the scope of the claimed subject matter.

Systems and methods are disclosed for determining a first downlinkcontrol indicator (DCI) and a second DCI, determining a set of activeaperiodic channel state information reference signals (A-CSI-RSs) basedon the first DCI, and determining a subset of the set of activeA-CSI-RSs based on the second DCI. Resource element (RE) muting may beperformed based on a set of active A-CSI-RSs. Channel state information(CSI) measurement may be performed based on a subset of a set of activeA-CSI-RSs. RE muting as disclosed herein may be puncturing orrate-matching around REs of a set of active A-CSI-RSs in order toreceive a physical downlink shared channel (PDSCH) transmission. Systemsand methods are further disclosed for determining at least one A-CSI-RSpattern based on a subset of a set of active A-CSI-RSs, where such atleast one A-CSI-RS pattern may be associated with a WTRU.

Systems and methods are disclosed for performing CSI measurement(s)based on a subset of a set of active A-CSI-RSs by performing the CSImeasurement(s) based on at least one A-CSI-RS pattern. Performing REmuting based on a set of active A-CSI-RSs may include performing mutingof at least one downlink transmission. A physical downlink controlchannel (PDCCH) common search space (CSS) may be monitored for detectionof a DCI that may be received via such a PDCCH CSS. An enhanced physicaldownlink control channel (EPDCCH) common search space (CSS) may bemonitored for detection of a DCI that may be received via such a EPDCCHCSS.

Systems and methods are disclosed for performing monitoring aWTRU-specific search space and determining a DCI based on theWTRU-specific search space. Determining a flag bit based on a DCI may beperformed, where such a flag bit may indicate whether the DCI includes asubset of a set of active A-CSI-RSs. RE muting may be performed based onat least one of a time or a frequency location.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of example examples is provided withreference to the appended drawings. For the purposes of illustration,the drawings show example examples. The contemplated subject matter isnot limited to the specific elements and/or instrumentalities describedor illustrated. Absent specific notation to the contrary, no subjectmatter is contemplated as necessary and/or essential. In addition, thedescribed examples may be employed in any combination, in whole or inpart. In the drawings:

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed examples may be implemented.

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A according to an example.

FIG. 1C is a system diagram illustrating an example radio access network(RAN) and an example core network (CN) that may be used within thecommunications system illustrated in FIG. 1A according to an example.

FIG. 1D is a system diagram illustrating a further example RAN and afurther example CN that may be used within the communications systemillustrated in FIG. 1A according to an example.

FIG. 2 is a diagram illustrating exemplary reference signals accordingto an example.

FIG. 3 is a diagram illustrating exemplary Enhanced Resource ElementGroups (EREG) according to an example.

FIG. 4 is a diagram illustrating exemplary resource elements (REs)according to an example.

FIG. 5 is a diagram illustrating exemplary reference signal (RS)configurations according to an example.

DETAILED DESCRIPTION

A detailed description of example examples will now be described withreference to the various figures. Although this description provides adetailed example of possible implementations, it should be noted thatthe details are intended to be examples and in no way limit the scope ofthe application. As used herein, the article “a” or “an,” absent furtherqualification or characterization, may be understood to mean “one ormore” or “at least one,” for example. Also, as used herein, the phrase“user equipment” (UE) may be understood to mean the same thing as thephrase “wireless transmit/receive unit” (WTRU).

FIG. 1A is a diagram illustrating an example communications system 100in which one or more disclosed examples may be implemented. Thecommunications system 100 may be a multiple access system that providescontent, such as voice, data, video, messaging, broadcast, etc., tomultiple wireless users. The communications system 100 may enablemultiple wireless users to access such content through the sharing ofsystem resources, including wireless bandwidth. For example, thecommunications systems 100 may employ one or more channel accessmethods, such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tailunique-word DFT-Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM(UW-OFDM), resource block-filtered OFDM, filter bank multicarrier(FBMC), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a RAN104/113, a CN 106/115, a public switched telephone network (PSTN) 108,the Internet 110, and other networks 112, though it will be appreciatedthat the disclosed examples contemplate any number of WTRUs, basestations, networks, and/or network elements. Each of the WTRUs 102 a,102 b, 102 c, 102 d may be any type of device configured to operateand/or communicate in a wireless environment. By way of example, theWTRUs 102 a, 102 b, 102 c, 102 d, any of which may be referred to as a“station” and/or a “STA”, may be configured to transmit and/or receivewireless signals and may include a user equipment (UE), a mobilestation, a fixed or mobile subscriber unit, a subscription-based unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watchor other wearable, a head-mounted display (HMD), a vehicle, a drone, amedical device and applications (e.g., remote surgery), an industrialdevice and applications (e.g., a robot and/or other wireless devicesoperating in an industrial and/or an automated processing chaincontexts), a consumer electronics device, a device operating oncommercial and/or industrial wireless networks, and the like. Any of theWTRUs 102 a, 102 b, 102 c and 102 d may be interchangeably referred toas a UE.

The communications systems 100 may also include a base station 114 aand/or a base station 114 b. Each of the base stations 114 a, 114 b maybe any type of device configured to wirelessly interface with at leastone of the WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to oneor more communication networks, such as the CN 106/115, the Internet110, and/or the other networks 112. By way of example, the base stations114 a, 114 b may be a base transceiver station (BTS), a Node-B, an eNodeB, a Home Node B, a Home eNode B, a gNB, a NR NodeB, a site controller,an access point (AP), a wireless router, and the like. While the basestations 114 a, 114 b are each depicted as a single element, it will beappreciated that the base stations 114 a, 114 b may include any numberof interconnected base stations and/or network elements.

The base station 114 a may be part of the RAN 104/113, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals on one or morecarrier frequencies, which may be referred to as a cell (not shown).These frequencies may be in licensed spectrum, unlicensed spectrum, or acombination of licensed and unlicensed spectrum. A cell may providecoverage for a wireless service to a specific geographical area that maybe relatively fixed or that may change over time. The cell may furtherbe divided into cell sectors. For example, the cell associated with thebase station 114 a may be divided into three sectors. Thus, in oneexample, the base station 114 a may include three transceivers, i.e.,one for each sector of the cell. In an example, the base station 114 amay employ multiple-input multiple output (MIMO) technology and mayutilize multiple transceivers for each sector of the cell. For example,beamforming may be used to transmit and/or receive signals in desiredspatial directions.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet(UV), visible light, etc.). The air interface 116 may be establishedusing any suitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104/113 and the WTRUs 102 a,102 b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 115/116/117 using wideband CDMA (WCDMA).WCDMA may include communication protocols such as High-Speed PacketAccess (HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-SpeedDownlink (DL) Packet Access (HSDPA) and/or High-Speed UL Packet Access(HSUPA).

In an example, the base station 114 a and the WTRUs 102 a, 102 b, 102 cmay implement a radio technology such as Evolved UMTS Terrestrial RadioAccess (E-UTRA), which may establish the air interface 116 using LongTerm Evolution (LTE) and/or LTE-Advanced (LTE-A) and/or LTE-Advanced Pro(LTE-A Pro).

In an example, the base station 114 a and the WTRUs 102 a, 102 b, 102 cmay implement a radio technology such as NR Radio Access, which mayestablish the air interface 116 using New Radio (NR).

In an example, the base station 114 a and the WTRUs 102 a, 102 b, 102 cmay implement multiple radio access technologies. For example, the basestation 114 a and the WTRUs 102 a, 102 b, 102 c may implement LTE radioaccess and NR radio access together, for instance using dualconnectivity (DC) principles. Thus, the air interface utilized by WTRUs102 a, 102 b, 102 c may be characterized by multiple types of radioaccess technologies and/or transmissions sent to/from multiple types ofbase stations (e.g., a eNB and a gNB).

In other examples, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.11 (e.g.,Wireless Fidelity (WiFi), IEEE 802.16 (e.g., Worldwide Interoperabilityfor Microwave Access (WiMAX)), CDMA2000, CDMA2000 1×, CDMA2000 EV-DO,Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), InterimStandard 856 (IS-856), Global System for Mobile communications (GSM),Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and thelike.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, an industrialfacility, an air corridor (e.g., for use by drones), a roadway, and thelike. In one example, the base station 114 b and the WTRUs 102 c, 102 dmay implement a radio technology such as IEEE 802.11 to establish awireless local area network (WLAN). In an example, the base station 114b and the WTRUs 102 c, 102 d may implement a radio technology such asIEEE 802.15 to establish a wireless personal area network (WPAN). In yetanother example, the base station 114 b and the WTRUs 102 c, 102 d mayutilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A,LTE-A Pro, NR etc.) to establish a picocell or femtocell. As shown inFIG. 1A, the base station 114 b may have a direct connection to theInternet 110. Thus, the base station 114 b may not be required to accessthe Internet 110 via the CN 106/115.

The RAN 104/113 may be in communication with the CN 106/115, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. The data may have varying qualityof service (QoS) requirements, such as differing throughputrequirements, latency requirements, error tolerance requirements,reliability requirements, data throughput requirements, mobilityrequirements, and the like. The CN 106/115 may provide call control,billing services, mobile location-based services, pre-paid calling,Internet connectivity, video distribution, etc., and/or performhigh-level security functions, such as user authentication. Although notshown in FIG. 1A, it will be appreciated that the RAN 104/113 and/or theCN 106/115 may be in direct or indirect communication with other RANsthat employ the same RAT as the RAN 104/113 or a different RAT. Forexample, in addition to being connected to the RAN 104/113, which may beutilizing a NR radio technology, the CN 106/115 may also be incommunication with another RAN (not shown) employing a GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

The CN 106/115 may also serve as a gateway for the WTRUs 102 a, 102 b,102 c, 102 d to access the PSTN 108, the Internet 110, and/or the othernetworks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) and/orthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired and/or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another CN connected to one or more RANs, whichmay employ the same RAT as the RAN 104/113 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities (e.g., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks). For example, the WTRU 102 c shown in FIG. 1A may be configuredto communicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram illustrating an example WTRU 102. As shownin FIG. 1B, the WTRU 102 may include a processor 118, a transceiver 120,a transmit/receive element 122, a speaker/microphone 124, a keypad 126,a display/touchpad 128, non-removable memory 130, removable memory 132,a power source 134, a global positioning system (GPS) chipset 136,and/or other peripherals 138, among others. It will be appreciated thatthe WTRU 102 may include any sub-combination of the foregoing elementswhile remaining consistent with an example.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in an example, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In an example, the transmit/receive element122 may be an emitter/detector configured to transmit and/or receive IR,UV, or visible light signals, for example. In yet another example, thetransmit/receive element 122 may be configured to transmit and/orreceive both RF and light signals. It will be appreciated that thetransmit/receive element 122 may be configured to transmit and/orreceive any combination of wireless signals.

Although the transmit/receive element 122 is depicted in FIG. 1B as asingle element, the WTRU 102 may include any number of transmit/receiveelements 122. More specifically, the WTRU 102 may employ MIMOtechnology. Thus, in one example, the WTRU 102 may include two or moretransmit/receive elements 122 (e.g., multiple antennas) for transmittingand receiving wireless signals over the air interface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as NR and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other examples, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anexample.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs and/or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, a Virtual Reality and/or Augmented Reality (VR/AR) device, anactivity tracker, and the like. The peripherals 138 may include one ormore sensors, the sensors may be one or more of a gyroscope, anaccelerometer, a hall effect sensor, a magnetometer, an orientationsensor, a proximity sensor, a temperature sensor, a time sensor; ageolocation sensor; an altimeter, a light sensor, a touch sensor, amagnetometer, a barometer, a gesture sensor, a biometric sensor, and/ora humidity sensor.

The WTRU 102 may include a full duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for both the UL (e.g., for transmission) anddownlink (e.g., for reception) may be concurrent and/or simultaneous.The full duplex radio may include an interference management unit 139 toreduce and or substantially eliminate self-interference via eitherhardware (e.g., a choke) or signal processing via a processor (e.g., aseparate processor (not shown) or via processor 118). In an example, theWTRU 102 may include a half-duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for either the UL (e.g., for transmission) or thedownlink (e.g., for reception)).

FIG. 1C is a system diagram illustrating the RAN 104 and the CN 106according to an example. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the CN 106.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an example. The eNode-Bs 160 a, 160 b, 160 cmay each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one example,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and/or receive wireless signals from, the WTRU 102a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the UL and/or DL, and the like. As shown in FIG. 1C, the eNode-Bs 160a, 160 b, 160 c may communicate with one another over an X2 interface.

The CN 106 shown in FIG. 1C may include a mobility management entity(MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN)gateway (or PGW) 166. While each of the foregoing elements are depictedas part of the CN 106, it will be appreciated that any of these elementsmay be owned and/or operated by an entity other than the CN operator.

The MME 162 may be connected to each of the eNode-Bs 162 a, 162 b, 162 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM and/or WCDMA.

The SGW 164 may be connected to each of the eNode Bs 160 a, 160 b, 160 cin the RAN 104 via the S1 interface. The SGW 164 may generally route andforward user data packets to/from the WTRUs 102 a, 102 b, 102 c. The SGW164 may perform other functions, such as anchoring user planes duringinter-eNode B handovers, triggering paging when DL data is available forthe WTRUs 102 a, 102 b, 102 c, managing and storing contexts of theWTRUs 102 a, 102 b, 102 c, and the like.

The SGW 164 may be connected to the PGW 166, which may provide the WTRUs102 a, 102 b, 102 c with access to packet-switched networks, such as theInternet 110, to facilitate communications between the WTRUs 102 a, 102b, 102 c and IP-enabled devices.

The CN 106 may facilitate communications with other networks. Forexample, the CN 106 may provide the WTRUs 102 a, 102 b, 102 c withaccess to circuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. For example, the CN 106 may include,or may communicate with, an IP gateway (e.g., an IP multimedia subsystem(IMS) server) that serves as an interface between the CN 106 and thePSTN 108. In addition, the CN 106 may provide the WTRUs 102 a, 102 b,102 c with access to the other networks 112, which may include otherwired and/or wireless networks that are owned and/or operated by otherservice providers.

Although the WTRU is described in FIGS. 1A-1D as a wireless terminal, itis contemplated that in certain representative examples that such aterminal may use (e.g., temporarily or permanently) wired communicationinterfaces with the communication network.

In representative examples, the other network 112 may be a WLAN.

A WLAN in Infrastructure Basic Service Set (BSS) mode may have an AccessPoint (AP) for the BSS and one or more stations (STAs) associated withthe AP. The AP may have an access or an interface to a DistributionSystem (DS) or another type of wired/wireless network that carriestraffic in to and/or out of the BSS. Traffic to STAs that originatesfrom outside the BSS may arrive through the AP and may be delivered tothe STAs. Traffic originating from STAs to destinations outside the BSSmay be sent to the AP to be delivered to respective destinations.Traffic between STAs within the BSS may be sent through the AP, forexample, where the source STA may send traffic to the AP and the AP maydeliver the traffic to the destination STA. The traffic between STAswithin a BSS may be considered and/or referred to as peer-to-peertraffic. The peer-to-peer traffic may be sent between (e.g., directlybetween) the source and destination STAs with a direct link setup (DLS).In certain representative examples, the DLS may use an 802.11e DLS or an802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) modemay not have an AP, and the STAs (e.g., all of the STAs) within or usingthe IBSS may communicate directly with each other. The IBSS mode ofcommunication may sometimes be referred to herein as an “ad-hoc” mode ofcommunication.

When using the 802.11ac infrastructure mode of operation or a similarmode of operations, the AP may transmit a beacon on a fixed channel,such as a primary channel. The primary channel may be a fixed width(e.g., 20 MHz wide bandwidth) or a dynamically set width via signaling.The primary channel may be the operating channel of the BSS and may beused by the STAs to establish a connection with the AP. In certainrepresentative examples, Carrier Sense Multiple Access with CollisionAvoidance (CSMA/CA) may be implemented, for example in in 802.11systems. For CSMA/CA, the STAs (e.g., every STA), including the AP, maysense the primary channel. If the primary channel is sensed/detectedand/or determined to be busy by a particular STA, the particular STA mayback off. One STA (e.g., only one station) may transmit at any giventime in a given BSS.

High Throughput (HT) STAs may use a 40 MHz wide channel forcommunication, for example, via a combination of the primary 20 MHzchannel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHzwide channel.

Very High Throughput (VHT) STAs may support 20 MHz, 40 MHz, 80 MHz,and/or 160 MHz wide channels. The 40 MHz, and/or 80 MHz, channels may beformed by combining contiguous 20 MHz channels. A 160 MHz channel may beformed by combining 8 contiguous 20 MHz channels, or by combining twonon-contiguous 80 MHz channels, which may be referred to as an 80+80configuration. For the 80+80 configuration, the data, after channelencoding, may be passed through a segment parser that may divide thedata into two streams. Inverse Fast Fourier Transform (IFFT) processing,and time domain processing, may be done on each stream separately. Thestreams may be mapped on to the two 80 MHz channels, and the data may betransmitted by a transmitting STA. At the receiver of the receiving STA,the above described operation for the 80+80 configuration may bereversed, and the combined data may be sent to the Medium Access Control(MAC).

Sub 1 GHz modes of operation are supported by 802.11af and 802.11ah. Thechannel operating bandwidths, and carriers, are reduced in 802.11af and802.11ah relative to those used in 802.11n, and 802.11ac. 802.11afsupports 5 MHz, 10 MHz and 20 MHz bandwidths in the TV White Space(TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and16 MHz bandwidths using non-TVWS spectrum. According to a representativeexample, 802.11ah may support Meter Type Control/Machine-TypeCommunications, such as MTC devices in a macro coverage area. MTCdevices may have certain capabilities, for example, limited capabilitiesincluding support for (e.g., only support for) certain and/or limitedbandwidths. The MTC devices may include a battery with a battery lifeabove a threshold (e.g., to maintain a very long battery life).

WLAN systems, which may support multiple channels, and channelbandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include achannel which may be designated as the primary channel. The primarychannel may have a bandwidth equal to the largest common operatingbandwidth supported by all STAs in the BSS. The bandwidth of the primarychannel may be set and/or limited by a STA, from among all STAs inoperating in a BSS, which supports the smallest bandwidth operatingmode. In the example of 802.11ah, the primary channel may be 1 MHz widefor STAs (e.g., MTC type devices) that support (e.g., only support) a 1MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4MHz, 8 MHz, 16 MHz, and/or other channel bandwidth operating modes.Carrier sensing and/or Network Allocation Vector (NAV) settings maydepend on the status of the primary channel. If the primary channel isbusy, for example, due to a STA (which supports only a 1 MHz operatingmode), transmitting to the AP, the entire available frequency bands maybe considered busy even though a majority of the frequency bands remainsidle and may be available.

In the United States, the available frequency bands, which may be usedby 802.11ah, are from 902 MHz to 928 MHz. In Korea, the availablefrequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the availablefrequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidthavailable for 802.11ah is 6 MHz to 26 MHz depending on the country code.

FIG. 1D is a system diagram illustrating the RAN 113 and the CN 115according to an example. As noted above, the RAN 113 may employ an NRradio technology to communicate with the WTRUs 102 a, 102 b, 102 c overthe air interface 116. The RAN 113 may also be in communication with theCN 115.

The RAN 113 may include gNBs 180 a, 180 b, 180 c, though it will beappreciated that the RAN 113 may include any number of gNBs whileremaining consistent with an example. The gNBs 180 a, 180 b, 180 c mayeach include one or more transceivers for communicating with the WTRUs102 a, 102 b, 102 c over the air interface 116. In one example, the gNBs180 a, 180 b, 180 c may implement MIMO technology. For example, gNBs 180a, 108 b may utilize beamforming to transmit signals to and/or receivesignals from the gNBs 180 a, 180 b, 180 c. Thus, the gNB 180 a, forexample, may use multiple antennas to transmit wireless signals to,and/or receive wireless signals from, the WTRU 102 a. In an example, thegNBs 180 a, 180 b, 180 c may implement carrier aggregation technology.For example, the gNB 180 a may transmit multiple component carriers tothe WTRU 102 a (not shown). A subset of these component carriers may beon unlicensed spectrum while the remaining component carriers may be onlicensed spectrum. In an example, the gNBs 180 a, 180 b, 180 c mayimplement Coordinated Multi-Point (CoMP) technology. For example, WTRU102 a may receive coordinated transmissions from gNB 180 a and gNB 180 b(and/or gNB 180 c).

The WTRUs 102 a, 102 b, 102 c may communicate with gNBs 180 a, 180 b,180 c using transmissions associated with a scalable numerology. Forexample, the OFDM symbol spacing and/or OFDM subcarrier spacing may varyfor different transmissions, different cells, and/or different portionsof the wireless transmission spectrum. The WTRUs 102 a, 102 b, 102 c maycommunicate with gNBs 180 a, 180 b, 180 c using subframe or transmissiontime intervals (TTIs) of various or scalable lengths (e.g., containingvarying number of OFDM symbols and/or lasting varying lengths ofabsolute time).

The gNBs 180 a, 180 b, 180 c may be configured to communicate with theWTRUs 102 a, 102 b, 102 c in a standalone configuration and/or anon-standalone configuration. In the standalone configuration, WTRUs 102a, 102 b, 102 c may communicate with gNBs 180 a, 180 b, 180 c withoutalso accessing other RANs (e.g., such as eNode-Bs 160 a, 160 b, 160 c).In the standalone configuration, WTRUs 102 a, 102 b, 102 c may utilizeone or more of gNBs 180 a, 180 b, 180 c as a mobility anchor point. Inthe standalone configuration, WTRUs 102 a, 102 b, 102 c may communicatewith gNBs 180 a, 180 b, 180 c using signals in an unlicensed band. In anon-standalone configuration WTRUs 102 a, 102 b, 102 c may communicatewith/connect to gNBs 180 a, 180 b, 180 c while also communicatingwith/connecting to another RAN such as eNode-Bs 160 a, 160 b, 160 c. Forexample, WTRUs 102 a, 102 b, 102 c may implement DC principles tocommunicate with one or more gNBs 180 a, 180 b, 180 c and one or moreeNode-Bs 160 a, 160 b, 160 c substantially simultaneously. In thenon-standalone configuration, eNode-Bs 160 a, 160 b, 160 c may serve asa mobility anchor for WTRUs 102 a, 102 b, 102 c and gNBs 180 a, 180 b,180 c may provide additional coverage and/or throughput for servicingWTRUs 102 a, 102 b, 102 c.

Each of the gNBs 180 a, 180 b, 180 c may be associated with a particularcell (not shown) and may be configured to handle radio resourcemanagement decisions, handover decisions, scheduling of users in the ULand/or DL, support of network slicing, dual connectivity, interworkingbetween NR and E-UTRA, routing of user plane data towards User PlaneFunction (UPF) 184 a, 184 b, routing of control plane informationtowards Access and Mobility Management Function (AMF) 182 a, 182 b andthe like. As shown in FIG. 1D, the gNBs 180 a, 180 b, 180 c maycommunicate with one another over an Xn interface.

The CN 115 shown in FIG. 1D may include at least one AMF 182 a, 182 b,at least one UPF 184 a,184 b, at least one Session Management Function(SMF) 183 a, 183 b, and possibly a Data Network (DN) 185 a, 185 b. Whileeach of the foregoing elements are depicted as part of the CN 115, itwill be appreciated that any of these elements may be owned and/oroperated by an entity other than the CN operator.

The AMF 182 a, 182 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 113 via an N2 interface and may serve as acontrol node. For example, the AMF 182 a, 182 b may be responsible forauthenticating users of the WTRUs 102 a, 102 b, 102 c, support fornetwork slicing (e.g., handling of different PDU sessions with differentrequirements), selecting a particular SMF 183 a, 183 b, management ofthe registration area, termination of NAS signaling, mobilitymanagement, and the like. Network slicing may be used by the AMF 182 a,182 b in order to customize CN support for WTRUs 102 a, 102 b, 102 cbased on the types of services being utilized WTRUs 102 a, 102 b, 102 c.For example, different network slices may be established for differentuse cases such as services relying on ultra-reliable low latency (URLLC)access, services relying on enhanced massive mobile broadband (eMBB)access, services for machine type communication (MTC) access, and/or thelike. The AMF 182 may provide a control plane function for switchingbetween the RAN 113 and other RANs (not shown) that employ other radiotechnologies, such as LTE, LTE-A, LTE-A Pro, and/or non-3GPP accesstechnologies such as WiFi.

The SMF 183 a, 183 b may be connected to an AMF 182 a, 182 b in the CN115 via an N11 interface. The SMF 183 a, 183 b may also be connected toa UPF 184 a, 184 b in the CN 115 via an N4 interface. The SMF 183 a, 183b may select and control the UPF 184 a, 184 b and configure the routingof traffic through the UPF 184 a, 184 b. The SMF 183 a, 183 b mayperform other functions, such as managing and allocating UE IP address,managing PDU sessions, controlling policy enforcement and QoS, providingdownlink data notifications, and the like. A PDU session type may beIP-based, non-IP based, Ethernet-based, and the like.

The UPF 184 a, 184 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 113 via an N3 interface, which may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between the WTRUs 102a, 102 b, 102 c and IP-enabled devices. The UPF 184, 184 b may performother functions, such as routing and forwarding packets, enforcing userplane policies, supporting multi-homed PDU sessions, handling user planeQoS, buffering downlink packets, providing mobility anchoring, and thelike.

The CN 115 may facilitate communications with other networks. Forexample, the CN 115 may include, or may communicate with, an IP gateway(e.g., an IP multimedia subsystem (IMS) server) that serves as aninterface between the CN 115 and the PSTN 108. In addition, the CN 115may provide the WTRUs 102 a, 102 b, 102 c with access to the othernetworks 112, which may include other wired and/or wireless networksthat are owned and/or operated by other service providers. In oneexample, the WTRUs 102 a, 102 b, 102 c may be connected to a local DataNetwork (DN) 185 a, 185 b through the UPF 184 a, 184 b via the N3interface to the UPF 184 a, 184 b and an N6 interface between the UPF184 a, 184 b and the DN 185 a, 185 b.

In view of FIGS. 1A-1D, and the corresponding description of FIGS.1A-1D, one or more, or all, of the functions described herein withregard to one or more of: WTRU 102 a-d, Base Station 114 a-b, eNode-B160 a-c, MME 162, SGW 164, PGW 166, gNB 180 a-c, AMF 182 a-b, UPF 184a-b, SMF 183 a-b, DN 185 a-b, and/or any other device(s) describedherein, may be performed by one or more emulation devices (not shown).The emulation devices may be one or more devices configured to emulateone or more, or all, of the functions described herein. For example, theemulation devices may be used to test other devices and/or to simulatenetwork and/or WTRU functions.

The emulation devices may be designed to implement one or more tests ofother devices in a lab environment and/or in an operator networkenvironment. For example, the one or more emulation devices may performthe one or more, or all, functions while being fully or partiallyimplemented and/or deployed as part of a wired and/or wirelesscommunication network in order to test other devices within thecommunication network. The one or more emulation devices may perform theone or more, or all, functions while being temporarilyimplemented/deployed as part of a wired and/or wireless communicationnetwork. The emulation device may be directly coupled to another devicefor purposes of testing and/or may performing testing using over-the-airwireless communications.

The one or more emulation devices may perform the one or more, includingall, functions while not being implemented/deployed as part of a wiredand/or wireless communication network. For example, the emulationdevices may be utilized in a testing scenario in a testing laboratoryand/or a non-deployed (e.g., testing) wired and/or wirelesscommunication network in order to implement testing of one or morecomponents. The one or more emulation devices may be test equipment.Direct RF coupling and/or wireless communications via RF circuitry(e.g., which may include one or more antennas) may be used by theemulation devices to transmit and/or receive data.

A WTRU may use one or more channel state information reference signals(CSI-RSs) in order to perform measurements. A CSI-RS may be transmittedusing a wideband (e.g., across the system bandwidth) with a duty cycle(e.g., 5, 10, 20, 40, 80 ms) that may be in a Physical Downlink SharedChannel (PDSCH) region. A number of CSI-RS patterns (e.g., 20 CSI-RSpatterns, less than 20 CSI-RS patterns, more than 20 CSI-RS patterns)may be available in a subframe. A CSI-RS pattern may be a CSI-RS reusepattern. A CSI-RS pattern may be a function a number of antenna portsthat may be in use at a transmitting device.

FIG. 2 illustrates diagrams 200 that include exemplary representationsof reference signals (RSs) 210, 220, 230. RSs 210, 220, 230 may includeCSI-RS patterns that may be based on a number of antenna ports that maybe used for transmission. In FIG. 2 , a same indication (e.g., sameshading illustrated in FIG. 2 ) of one or more resource elements (REs)in each illustrated RS may indicate a set of one or more REs that may beassociated with a CSI-RS configuration and/or a CSI-RS pattern. Notethat in the instant disclosure, CSI-RS pattern, CSI-RS reuse pattern,CSI-RS pattern reuse, and CSI-RS configuration may be usedinterchangeably.

In FIG. 2 , example CSI-RS patterns for each of 2 (e.g., RS 210), 4(e.g., RS 220), and 8 (e.g., RS 230) antenna ports are shown. One ormore CSI-RS reuse patterns of such 2, 4, and 8 antenna ports may beaggregated to form a CSI-RS pattern, for example, where more than 8antenna ports may be used.

CSI-RS configurations may refer to the configuration of one or morereference signals to be transmitted for purposes of CSI measurements.The examples described herein may be set forth in terms of a WTRUreceiving a CSI-RS configuration that define one or more referencesignals to be transmitted by the WTRU in the uplink; however, the WTRUmay also receive a CSI-RS configuration that defines one or morereference signals to be received in the downlink. For example, the WTRUmay receive a first CSI-RS configuration that defines one or moreCSI-RSs (e.g., time/frequency location, power level, periodicity,frequency hopping pattern, code, etc.). The WTRU may then transmit theCSI-RS(s) in accordance with the configuration, for example eitherperiodically and/or aperiodically based on a trigger. The trigger mayindicate which portions of the CSI configuration is applicable to agiven aperiodic CSI-RS transmission. For example, the trigger (e.g.,DCI) may indicate whether the CSI-RS are to be transmitted using anon-zero power RS or with a zero-power CSI RS (e.g., muting is to beperformed).

In an example of the WTRU receiving a downlink CSI-RS, the WTRU mayreceive a second CSI-RS configuration that defines one or more CSI-RSs(e.g., time/frequency location, power level, periodicity, frequencyhopping pattern, code, etc.). The WTRU may then receive the CSI-RS(s) inaccordance with the configuration, for example either periodicallyand/or aperiodically based on a trigger. The trigger may indicate whichportions of the CSI configuration is applicable to a given aperiodicCSI-RS transmission. For example, the trigger (e.g., DCI) may indicatewhether the CSI-RS are to be received in accordance with a first CSI-RSpattern or in accordance with a second CSI-RS pattern.

In an example, the WTRU receive a CSI-RS configuration that defines aplurality of possible CSI-RS transmissions, for example CSI-RS downlinktransmissions. In some subframes, each of the possible CSI-RStransmissions may be performed, for example by the eNB transmitting theCSI-RS transmissions in accordance with the CSI-RS configuration. A DCImay be used to indicate to the WTRU that the eNB will be transmittingthe CSI-RS transmissions in accordance with the CSI-RS configuration inthat subframe. In an example, not all of the CSI-RS transmissions to besent by the WTRU may be applicable to the WTRU or otherwise may not bemeasured by the WTRU. For example, a first DCI may be used to indicate aplurality of CSI-RSs that are active for a subframe. A second DCI mayindicate a subset of the plurality of CSI-RSs that are active and thatshould be measure by the WTRU. The WTRU may use the first and secondDCIs to determine which of the plurality of CSI-RSs should be measured(e.g., the indicated subset) and which of the plurality of CSI-RSsshould be muted (e.g., the active set minus the indicated subset). TheWTRU may performing muting of the REs that include active CSI-RSs thatare not being measured by the WTRU by performing rate matching and/orother techniques described herein for those resource elements. The ratematching may be performed in order to receive a PDSCH transmission thatincludes that resource elements to be muted.

Note that, as used herein, “DCI” may refer to “downlink controlindicator” or “downlink control information.” “Downlink controlindicator,” “downlink control information,” and “DCI” may be usedinterchangeably herein.

One or more channels and/or channel types may be used for reporting CSIfeedback. For example, either or both of a Physical Uplink ControlChannel (PUCCH) or a Physical Uplink Shared Channel (PUSCH) may be usedfor reporting CSI feedback. A PUCCH channel may, for example, provideCSI feedback while, e.g., utilizing limited feedback overhead. A PUSCHchannel may, for example, provide a relatively large amount of feedbackoverhead while, e.g., providing relatively lower reliability. A PUCCHchannel may be used for periodic CSI feedback, for example, where coarselink adaptation may be in use. A PUSCH channel may be used upon atriggering of aperiodic CSI reporting, for example, where finer linkadaptation may be in use.

CSI feedback may include (e.g., may be reported in a format that mayinclude) at least one of a rank indicator (RI), a precoder matrix index(PMI), and a channel quality indicator (CQI). An RI and/or a PMI may becalculated at a WTRU receiver, for example, by such a WTRU selecting arank and/or a precoding matrix (e.g., from a predefined codebook) thatmay increase WTRU throughput. A PMI and/or a CQI may be assigned toand/or reported as associated with one or more categories, such aswideband, subband, and a WTRU-selected subband. An RI may (e.g., mayonly) be reported using wideband. Table 1 illustrates example schedulingmodes that may be associated with PUCCH and/or PUSCH. Table 2illustrates example values that may be used for CSI feedback accordingto a transmission mode and/or a reporting mode (e.g., periodic oraperiodic).

TABLE 1 Reporting modes in LTE and/or LTE-A Periodic CSI Aperiodic CSIScheduling reporting reporting Mode channels channel Frequency non-PUCCH selective Frequency selective PUCCH PUSCH

TABLE 2 CSI feedback information according to reporting modesTransmission Mode Aperiodic Feedback Periodic Feedback 1 Mode 2-0: WTRUselected Mode 1-0: WB CQI 2 sub band CQI: WB CQI + Mode 2-0: WTRUSelected sub 3 CQI over M best subbands band CQI: WB CQI + WTRU 7 Mode3-0: high layer (HL) reports CQI in preferred subband in configuredsubband CQI: WB each BW part, one BW part in each 8 CQI + subband CQIreporting opportunity Notes: Notes: CQI for first CW only, No CQI forfirst CW only, No PMI PMI 4 Mode 1-2: WB CQI/Multiple Mode 1-1: WBCQI/Single PMI 6 PMI: CQI for each CW; PMI Mode 2-1: WTRU selectedsubband for each subband CQI/Single PMI (N_(RB) ^(DL) > 7 only): Mode2-2: WTRU selected WB CQI/PMI + WTRU reports 8 sub band CQI/MultiplePMI: CQI in preferred subband in each CQI per CW and PMI, both BW partover full BW and M best subbands Mode 3-1: HL configured sub bandCQI/Single PMI: WB CQI + subband CQI, both per CW 5 Mode 3-1: HLconfigured sub band CQI/Single PMI (see above)

Periodic and/or aperiodic feedback (e.g., CSI feedback) may betransmitted on a PUCCH channel. Periodic and/or aperiodic feedback mayalso, or instead, be transmitted on a PUSCH channel, for example, when aPUSCH channel allocation has been provided to the WTRU and/or isotherwise available.

Periodic reporting may use one or more types of reports and/or one ormore sequences of one or more types of reports. A report type may be oneor more of, for example, report type 1 (e.g., that may be associatedwith subband CQI), report type 2 (e.g., that may be associated withwideband CQI/PMI), report type 3 (e.g., that may be associated with RI)and/or report type 4 (e.g., that may be associated with wideband CQI).

Aperiodic CSI (e.g., CSI feedback) may be requested, for example, by anuplink grant (e.g., downlink control indicator (DCI) format 0, DCIformat 4). Aperiodic CSI (e.g., CSI feedback) may be requested, forexample, when a CQI Request bit may be set in an associated DCI.Aperiodic CSI (e.g., CSI feedback) may be transmitted, for example, on aPUSCH.

A CSI report type (e.g., a periodic CSI report type) may include one ormore of report types, for example, when eight (8) transmit (Tx) antennaports may be used. Such report types may include one or more of a type 1report (e.g., that may support CQI feedback for WTRU selected sub-bands)and a type 1a report (e.g., that may support subband CQI and/or secondPMI feedback). Such report types may also, or instead, include one ormore of a type 2, type 2b, and/or a type 2c reports (e.g., each of whichmay support wideband CQI and/or PMI feedback). Such report types mayalso, or instead, include one or more of a type 2a report (e.g., thatmay support wideband PMI feedback), a type 3 report (e.g., that maysupport RI feedback), a type 4 report (e.g., that may support widebandCQI), a type 5 report (e.g., that may support RI and/or wideband PMIfeedback), and a type 6 report (e.g., that may support RI and/or PTIfeedback).

An exemplary type 6 report may include and/or use a precoding typeindicator (PTI) for eight (8) transmit antenna ports, for example, wherean 8Tx (eight transmit ports) precoder may be defined with a dualcodebook.

RE muting may be used, for example, to avoid a collision of signals.Where RE muting may be used, puncturing and/or rate-matching may beused, for example, from a coding chain perspective. Where puncturing maybe used, a signal that may be mapped to a punctured RE may not betransmitted and/or may be transmitted at zero (0) power in such apunctured RE. Where rate-matching may be used, a mapping of one or moresignals to one or more REs may help avoid mapping to one or moreparticular REs, which may, for example, result in other signals notbeing transmitted.

An N-bit coded bit sequence for a channel, for example (c₁, . . . ,c_(N)), may be an output of a channel encoder that may have a payloadand/or information as an input. Such a channel encoder may use anychannel code, such as turbo code, convolutional code, Reed-Muller code,etc. Such a coded bit sequence may be an input to a mapper.

An M-symbol modulated symbol sequence, for example (x₁, . . . , x_(M)),may be an output of a mapper where a coded bit sequence may be modulatedaccording to a modulation scheme (e.g., binary phase-shift keying(BPSK), quadrature phase-shift keying (QPSK), 16 quadrature amplitudemodulation (16QAM), 64 quadrature amplitude modulation (64QAM)). Amodulated symbol sequence of length M may be equal to or smaller than N,for example, based on a modulation scheme that may be used.

A modulated symbol sequence may be mapped to a set of one or more REsfor a channel, for example, according to a predefined order. Forexample, x₁, . . . , x_(M) may be mapped onto M REs that may be used fora channel in a certain order, e.g., a predefined order. If a k-th (e.g.,where k≤M) RE may be muted (e.g., due to a collision), puncturing mayindicate that a modulated symbol x_(k) may not be transmitted.Rate-matching may indicate that a mapping may skip one or more REs thatmay be muted and/or that fewer modulated symbols may be mapped.

M-1 modulated symbol(s) may be mapped and/or transmitted for one or morerate-matched REs. For example, x₁, . . . , x_(M) may be transmitted anda last modulated symbol may not be transmitted based on a muting of thek-th RE. Puncturing may lose coded bits in positions of muted REs.Rate-matching may lose coded bits from last coded bits.

RE muting with puncturing may be referred to as “RE puncturing” herein.RE muting with rate-matching may be referred to as “RE rate-matching”herein. As used herein, RE muting may include either or both of REpuncturing and RE rate-matching.

RE muting (e.g., in an LTE system) may be performed, for example, toavoid a collision between signals of different types in a samedirection. For example, in a downlink (DL), PDSCH REs may be muted toavoid a collision with one or more CSI-RSs and/or one or morepositioning reference signal (PRS) REs. Such CSI-RSs and/or PRS REs maybe muted to avoid a collision with a primary synchronization signal(PSS) and/or a secondary synchronization signal (SSS). An uplink channel(UL) that may use PUSCH and/or PUCCH may be shortened in an effort toavoid a collision with a sounding reference signal (SRS) in the UL.

An Enhanced Physical Downlink Control Channel (EPDCCH) may be used toachieve frequency domain inter-cell interference coordination (ICIC)and/or beamforming gain. EPDCCH, ePDCCH, and E-PDCCH may be usedinterchangeably herein. Enhanced Resource Element Group (EREG) andEnhanced Control Channel Element (ECCE) may be used interchangeablyherein, and may also be referred to as eREG and eCCE, respectively. Forexample, since a plurality of EREGs may be used to form an ECCE, theEPDCCH resources may be equivalently described either in terms of EREGsor ECCEs

EPDCCH resources for a WTRU-specific search space may be configured witha subset of physical resource blocks (PRBs) in a PDSCH region. EPDCCHresources may be configured in a WTRU-specific manner. EPDCCH resourcesets (e.g., up to two EPDCCH resource sets) may be configured for aWTRU. An EPDCCH resource set may be configured with 2, 4, or 8PRB-pairs. An EPDCCH resource set may be determined as a localizedresource set and/or a distributed resource set.

One or more PRB-pairs may be configured as an EPDCCH resource. In eachsuch PRB-pair, a number of EREGs may be defined. For example, sixteen(16) EREGs may be defined for each such PRB-pair, for example,regardless of associated Cyclic Prefix (CP) length (e.g., normal CP,extended CP).

FIG. 3 illustrates exemplary eREG definitions 300 of a PRB-pair in a CPsubframe. REs for such an eREG may be allocated cyclically in afrequency first manner and/or may be rate-matched based on ademodulation reference signal (DM-RS) (e.g., antenna ports 307, 308,309, 310 shown in FIG. 3 ). This may result in randomizing channelestimation performance across eREGs as channel estimation performancemay be different according to an RE's location in a PRB-pair.

An ECCE may be defined by, for example, a grouping of four (4) or eight(8) EREGs that may be within an EPDCCH resource set. A total number ofECCEs (may be indicated as N_(eCCE,set)) in an EPDCCH resource set maybe determined as a function of a number of PRB pairs (may be indicatedas N_(PRB,set)) that may be configured for such an EPDCCH resource setand/or a number of EREGs that may be grouped for an ECCE (may beindicated as N_(eREG)). For example,N_(eCCE,set)=16×N_(PRB,set)/N_(eREG). EREGs for an ECCE may be mutuallyexclusive for EREGs that may be associated with another ECCE.

Two or more types of ECCEs may be determined based on an operation modeof an EPDCCH resource set (e.g., localized mode of operation,distributed mode of operation). An ECCE for a localized mode ofoperation may be referred to as a localized ECCE (L-ECCE). An ECCE for adistributed mode of operation may be referred to as a distributed ECCE(D-ECCE).

To form an L-ECCE, multiple EREGs (e.g., four (4) or eight (8) EREGs)that may be located in a same PRB-pair may be grouped together.

EREGs in different PRB-pairs may be grouped to form a D-ECCE.

EREGs in an EPDCCH resource set may be used to form an L-ECCE and/or aD-ECCE based on an operation mode of the EPDCCH that may be configuredfor an associated EPDCCH resource set. For example, an EPDCCH resourceset may be configured with a localized operation mode (e.g., localizedEPDCCH). EREGs in such an EPDCCH resource set may be used to formL-ECCEs. An EPDCCH resource set may include ECCEs that may be eitherL-ECCEs or D-ECCEs.

Table 3 illustrates exemplary numbers of EREGs that may be grouped toform an ECCE based on exemplary subframe configurations. For example,four (4) EREGs may be grouped to form an ECCE, e.g., for a normalsubframe and/or a special subframe configuration 3, 4, 8 in timedivision duplexing TDD where sufficient numbers of REs may be availableper ECCE such that a particular effective coding rate may be used.

Table 3 further illustrates exemplary number of eight (8) EREGs that maybe grouped to form an ECCE, e.g., for a normal subframe and/or a specialsubframe configuration 1, 2, 6, 7, 9 and/or a special subframeconfiguration 1, 2, 3, 5, 6 in time division duplexing TDD, wheresufficient numbers of REs may be available per ECCE such that aparticular effective coding rate may be used.

TABLE 3 Example numbers of grouped EREGs per ECCE Normal cyclic prefixExtended cyclic prefix Special Special Special subframe, subframe,subframe, Normal configuration configuration Normal configurationsubframe 3, 4, 8 1, 2, 6, 7, 9 subframe 1, 2, 3, 5, 6 Number of groupedNumber of grouped EREGs: 8 EREGs: 4

A WTRU-specific search space may be used with EPDCCH. Common searchspace may be located (e.g., always located) at a PDCCH region. WTRUmonitoring behavior for downlink control signaling reception may bedefined in a downlink subframe as a WTRU monitoring WTRU-specific searchspace in EPDCCH and common search space in PDCCH, where a EPDCCHmonitoring subframe may be configured via higher layer signaling. WTRUmonitoring behavior for downlink control signaling reception may also,or instead, be defined in a downlink subframe as a WTRU monitoring bothWTRU-specific search space and common search space in PDCCH. Where asubframe may be configured to monitor an EPDCCH subframe, if EPDCCH maynot be available in such a subframe due to, for example, collisionsbetween EPDCCH REs and other signals, a WTRU-specific search spacefallback may be used so that a WTRU may monitor PDCCH for WTRU-specificsearch space.

Table 4 illustrates exemplary EPDCCH formats in terms of aggregationlevels (e.g., N_(ECCE)) that may be a function of a number of availableREs (n_(EPDCCH)) for EPDCCH in a PRB-pair. Where an available number ofREs may be less than a threshold (e.g., n_(EPDCCH)<104), an aggregationlevel may increase in an effort to maintain a similar effective codingrate. For example, one or more supportable EPDCCH formats that may beused for localized transmission where n_(EPDCCH)<104 may be N_(ECCE)∈{2,4,8,16}, while N_(ECCE) ∈{1,2,4,8} may be used in other cases (e.g.,where n_(EPDCCH)≥104). A set of aggregation levels may be based onEPDCCH transmission modes.

TABLE 4 Examples of supported EPDCCH formats N_(ECCE) Normal subframesand special subframes, configuration 3, 4, 8, with n_(EPDCCH) < 104 andusing normal cyclic prefix All other cases EPDCCH Localized DistributedLocalized Distributed format transmission transmission transmissiontransmission 0 2 2 1 1 1 4 4 2 2 2 8 8 4 4 3 16 16 8 8 4 — 32 — 16

EPDCCH REs may be defined as REs in a PRB-pair. EPDCCH REs may be REsthat may not be occupied by antenna ports such as antenna ports {407,408, 409, 410} shown in FIG. 4 as components of example EPDCCH REdefinitions 420 and 430 illustrated in block diagram 400.

FIG. 4 illustrates exemplary EPDCCH RE definitions 420 and 430 for aPRB-pair based on a CP length without collision with other signals. Aresult in such an example may be 144 available REs (as shown in EPDCCHRE definition 420) and/or 128 available REs (as shown in EPDCCH REdefinition 430) for normal CP and extended CP, respectively.

EPDCCH resources may be configured in a PDSCH region so that REs for anEPDCCH may collide with one or more other signals, such as, but notlimited to, CSI-RS, CRS, PRS, PBCH, SCH, and PDCCH. WTRU behaviors whenREs collide with one or more other signals may include rate-matchingcoded bits for an EPDCCH around for the REs colliding with CSI-RS, CRS,and/or PDCCH. WTRU behaviors when REs collide with one or more othersignals may also, or instead, include using a PRB-pair for PBCH and SCHin a subframe that may not be used for EPDCCH. If other signals may betransmitted in a PRB-pair configured for EPDCCH, available REs forEPDCCH may be reduced.

A WTRU may monitor and/or attempt to decode a set of EPDCCH candidatesin a subframe or TTI, where an EPDCCH candidate may be determined basedon an ECCE aggregation level, a starting ECCE number, and/or a mode ofoperation (e.g., localized, distributed). The terms “EPDCCH candidate”and “EPDCCH decoding candidate” may be used interchangeably herein.

A set of EPDCCH candidates for a WTRU-specific search space may bedetermined in a WTRU-specific manner. A set of EPDCCH candidates for acommon search space may be determined in a cell-specific manner.

A set of ECCE aggregation levels that may be associated with EDCCHcandidates in an EPDCCH search space may be determined as a function ofat least one of a number of PRB-pairs configured for an EPDCCH resourceset, available REs (n_(EPDCCH)) in a subframe, an EPDCCH search spacetype (e.g., common search space, WTRU-specific search space), a subframetype (e.g., normal subframe, special subframe), a cyclic prefix (CP)length (e.g., normal CP, extended CP), and/or an EPDCCH operation mode(e.g., localized, distributed).

Tables 5 and 6 provide examples of a set of ECCE aggregation levels (L)and an associated number of EPDCCH candidates for each ECCE aggregationlevel in an EPDCCH search space according to a number of PRB-pairs(N_(RB) ^(X) ^(p) ) configured for an EPDCCH resource set.

TABLE 5 Example set of EPDCCH candidates that may be monitored by a WTRUfor a distributed EPDCCH according to a number of available REs(n_(EPDCCH)) Number of EPDCCH candidates Number of EPDCCH candidatesM_(p) ^((L)) for n_(EPDCCH) < 104 M_(p) ^((L)) for n_(EPDCCH) ≥ 104N_(RB) ^(Xp) L = 2 L = 4 L = 8 L = 16 L = 32 L = 1 L = 2 L = 4 L = 8 L =16 2 4 2 1 0 0 4 2 1 0 0 4 8 4 2 1 0 8 4 2 1 0 8 6 4 3 2 1 6 4 3 2 1

TABLE 6 Example number of EPDCCH candidates that may be monitored by aWTRU for a localized EPDCCH according to a number of available REs(n_(EPDCCH)) Number of EPDCCH candidates Number of EPDCCH candidatesM_(p) ^((L)) for n_(EPDCCH) < 104 M_(p) ^((L)) for n_(EPDCCH) ≥ 104N_(RB) ^(Xp) L = 2 L = 4 L = 8 L = 16 L = 1 L = 2 L = 4 L = 8 2 4 2 1 04 2 1 0 4 8 4 2 1 8 4 2 1 8 6 6 2 2 6 6 2 2

A CSI-RS transmission may be used for a measurement of CSI and/or forCSI reporting. A CSI-RS transmission may be (in some examples, only)transmitted in a periodic manner, for example, according to a higherlayer configuration. When a WTRU may be triggered for CSI reporting, theWTRU may (in some examples, already) have CSI configuration informationfor CSI reporting. Periodic CSI-RS transmission may, for example,require more reference signal overhead and/or provide less flexibilitythan using a WTRU-specific CSI-RS transmission.

Aperiodic CSI-RS transmission may be used to reduce reference signaloverhead. An aperiodic CRS-RS transmission may be used for aperiodic CSIreporting. A presence of an aperiodic CSI-RS may be indicateddynamically for aperiodic CSI-RS reporting. Performance of downlinkchannels in a subframe that may contain aperiodic CSI-RS may, forexample, be degraded. An aperiodic CSI-RS may interfere with otherdownlink channels, for example, when a WTRU may not be aware of apresence of an aperiodic CSI-RS. For example, a WTRU may fail to receivea dynamic indication of an aperiodic CSI-RS presence. Such a WTRU mayfail to receive other downlink channels in a same subframe as well.

A WTRU may be configured to monitor EPDCCH. Such a WTRU may not be ableto receive an indication of an aperiodic CSI-RS presence before the WTRUmay start attempting to decode a configured EPDCCH search space, forexample, where a dynamic indication of an aperiodic CSI-RS presence maybe signaled in the EPDCCH search space. Performance of EPDCCH maythereby be degraded.

Aperiodic (e.g., triggered) CSI-RS transmission and/or reporting mayimprove flexibility of CSI-RS transmission in a WTRU-specific manner.CSI-RS transmission and/or associated CSI reporting may be based ontriggering, for example, eNodeB triggering.

An eNodeB may trigger an aperiodic CSI reporting in a subframe (e.g.,subframe n). Such a subframe's associated measurement reference signal(e.g., CSI-RS) may be transmitted in the same subframe (e.g., subframen) and/or in one or more adjacent subframes (e.g., subframe n−2, n−1,n+1, n+2, etc.).

Triggering of aperiodic CSI reporting may be based on an indication thatmay be signaled, monitored, and/or decoded (e.g., by a WTRU) in asubframe or a subset of subframes. An indication of aperiodic CSIreporting triggering may be an implicit indication or an explicitindication.

The terms “aperiodic CSI reporting,” “A-CSI reporting,” “A-CSI,” “CSIreporting triggered,” “triggering based CSI reporting,” “PUSCH based CSIreporting,” “CSI reporting on PUSCH,” “CSI reporting based on a dynamicindication,” “indication based CSI reporting,” and “one shot CSIreporting” may be used interchangeably herein. The terms “subframe,”“transmission time interval (TTI),” and “time unit for a transmission”may also be used interchangeably herein. The terms “aperiodicmeasurement reference signal,” “triggered measurement reference signal,”“CSI-RS,” “aperiodic CSI-RS,” “aperiodic CSI-IM,” “A-CSI-IM,”“A-CSI-RS,” “triggering based CSI-RS,” “one shot CSI-RS,” “dynamicindication based CSI-RS,” “CSI-RS resource indicated in downlink controlindicator (DCI),” and “CSI-RS associated with an A-CSI only” may also beused interchangeably herein. The terms “A-CSI-RS,” “RE location ofA-CSI-RS in a subframe,” “A-CSI-RS configuration,” “time and frequencylocation of A-CSI-RS,” “A-CSI-RS pattern,” “A-CSI-RS reuse pattern,” and“A-CSI-RS locations” may also be used interchangeably herein.

An associated measurement reference signal for A-CSI reporting may betransmitted, signaled, received, and/or measured (e.g., by a WTRU)aperiodically. An aperiodic measurement reference signal for A-CSIreporting may be referred to as “aperiodic CSI-RS” herein.

A CSI-RS transmitted periodically may be referred to as “P-CSI-RS” andused interchangeably with a CSI-RS configured by a higher layer. Apresence of a P-CSI-RS in a subframe may be known to a WTRU before sucha WTRU may start receiving a signal from the subframe. A CSI-RStransmitted aperiodically may be referred to as “A-CSI-RS.” A presenceof an A-CSI-RS in a subframe may be determined based on a dynamicindication. A dynamic indication for a presence of an A-CSI-RS may beassociated with one or more subframes. A dynamic indication for apresence of A-CSI-RS may be used for activation and/or deactivation ofan A-CSI-RS. For example, such an indication may activate an A-CSI-RS,which may be transmitted periodically until deactivated.

A full CSI configuration (e.g., full CSI configuration information) maybe configured via a higher layer (e.g., RRC signaling), for example forP-CSI-RS. A full CSI configuration may include, for example, one or moreof a CSI-RS pattern, a number of CSI processes, a duty cycle of CSI-RStransmission, a number of CSI-RS ports, a time/frequency locations ofCSI-RS, and a transmission power of a CSI-RS.

A partial CSI configuration (e.g., partial CSI configurationinformation) may be configured via a higher layer (e.g., RRC signaling),for example for A-CSI-RS. A partial CSI-RS configuration may include asubset of a full CSI configuration. A partial CSI-RS configuration mayinclude, for example, one or more CSI-RS patterns and/or one or moreindications thereof. A subset of a full CSI configuration or a partialCSI configuration may be indicated dynamically, for example, from a DCI(e.g., a DCI that may trigger A-CSI reporting). In an example, a DCI mayindicate that one or more portions of a CSI configuration (e.g., full orpartial) may be applicable to a given CSI-RS transmission. For example,at least one CSI-RS pattern that may be used in a subframe and/or apresence of a configured CSI-RS pattern may be dynamically indicated(e.g., from a DCI).

One or more A-CSI-RSs may be indicated to a WTRU in a subframe. AnA-CSI-RS may be categorized into a type, for example from among two ormore types. A first type of an A-CSI-RS may be used for CSI measurementand/or RE muting of one or more other physical channels. Such a firsttype of an A-CSI-RS may be a non-zero-power A-CSI-RS for a WTRU. Such afirst type of an A-CSI-RS for a first WTRU may be considered,determined, and/or used as a second type of an A-CSI-RS for a secondWTRU.

A second type of an A-CSI-RS may be used for RE muting of one or moreother downlink physical channels, in some examples, only for RE mutingof one or more downlink physical channels. Such RE muting may bepuncturing and/or rate-matching. A second type of an A-CSI-RS may be azero-power A-CSI-RS for a WTRU. RE muting may correspond to a WTRUrefraining from and/or attempting to refrain from transmitting anysignal energy on the A-CSI-RS resources. A second type of an A-CSI-RSfor a first WTRU may be considered, determined, and/or used as a firsttype of an A-CSI-RS for a second WTRU.

A first type of an A-CSI-RS may be referred to as a “Type-1 A-CSI-RS”herein. A second example type of an A-CSI-RS may be referred to as“Type-2 A-CSI-RS” herein.

A WTRU may receive an indication of one or more Type-1 A-CSI-RSs. Such aWTRU may measure CSI from the indicated one or more Type-1 A-CSI-RSs andconsider, determine, and/or assume that each RE(s) occupied by one ormore Type-1 A-CSI-RS(s) may be a muted RE for reception of one or moredownlink channels (e.g., PDSCH, EPDCCH) that may be scheduled for theWTRU.

A WTRU may receive an indication of one or more Type-2 A-CSI-RSs. Such aWTRU may consider, determine, and/or assume that each RE(s) occupied byone or more Type-2 A-CSI-RS may be a muted RE for reception of downlinkchannels that may be scheduled for the WTRU. For example, a WTRU may bescheduled for a PDSCH in a subframe and such a WTRU may receive anindication that one or more Type-2 A-CSI-RS may be in the same subframe.Such a WTRU may consider each RE(s) occupied by the indicated Type-2A-CSI-RS as a muted RE for scheduled PDSCH reception.

A WTRU may be configured with one or more A-CSI-RSs and/or one or moreP-CSI-RS s for CSI reporting and/or RE muting of one or more downlinkphysical channels. A CSI-RS configuration for an A-CSI-RS may differfrom a CSI-RS configuration for an

P-CSI-RS. A CSI-RS configuration may include at least one of, but notlimited to, a number of antenna ports, a scrambling sequence, a dutycycle, a starting offset, a transmission power, and a reuse pattern.

A WTRU may be indicated, configured, and/or determined to receive,measure, and/or handle one or more A-CSI-RSs and/or one or moreP-CSI-RSs in a same subframe. For example, a WTRU may be configured witha P-CSI-RS for CSI reporting and may be indicated to receive and/ormeasure an A-CSI-RS in a subframe in which the configured P-CSI-RS maybe transmitted.

A WTRU may measure an A-CSI based on a P-CSI-RS. Such a WTRU may beindicated to report A-CSI in a subframe in which no A-CSI-RS may beindicated. A P-CSI-RS for such an A-CSI measurement may be located inthe same subframe or in a previous subframe. A WTRU may be indicated toreport A-CSI in a subframe and the WTRU may assume that an A-CSI-RS maybe transmitted in the subframe.

A WTRU may be indicated independently for each of an A-CSI reportingrequest and an A-CSI-RS indication, where such an A-CSI-RS indicationmay include at least one indication of a presence or absence of anA-CSI-RS, configuration information of an A-CSI-RS, and an A-CSI-RSconfiguration index.

A bit field may be used to indicate an A-CSI reporting request and/or anA-CSI-RS presence indication. For example, one or more states from a bitfield may be indicated to trigger A-CSI reporting and/or to indicatepresence of one or more A-CSI-RS(s). Two bits may be used to indicate anA-CSI reporting trigger and an A-CSI-RS presence indication (e.g., 00may indicate an A-CSI reporting trigger with an A-CSI-RS absence, 01 mayindicate an A-CSI reporting trigger with an A-CSI-RS presence, 10 mayindicate no A-CSI trigger and an A-CSI-RS presence, 11 may be reserved).An indication of an A-CSI-RS presence without an A-CSI trigger may beused to indicate that RE muting may be performed for one or more otherphysical channels.

A bit field for a Type-1 A-CSI-RS indication may be located and/or usedin a DCI associated with uplink transmission (e.g., DCI format 0/4). Abit field for a Type-2 A-CSI-RS indication may be located and/or used ina DCI associated with downlink transmission (e.g., DCI formats1/2/2A/2B/2C).

A bit field for a Type-1 A-CSI-RS indication may be located in a DCIassociated with an uplink grant. A bit field for both a Type-1 and aType-2 A-CSI-RS indication may be located and/or used in a DCI that maybe dedicated to A-CSI-RS indication. A bit field for both a Type-1 and aType-2 A-CSI-RS indication may be used as an indication of a superset ofA-CSI-RS configurations in a subframe. A bit field in a DCI associatedwith an uplink grant that may indicate a Type-1 A-CSI-RS may be used asa subset of A-CSI-RS configurations.

A bit field for one or more A-CSI-RS configurations, which may be used(e.g., commonly) for one or more WTRUs in a subframe, may be locatedand/or used in a common DCI, where such a common DCI may be monitored byone or more WTRUs. A WTRU may receive one or more Type-1 A-CSI-RSindications in a WTRU-specific DCI (e.g., DCI format 0/4) in a samesubframe. Indicated Type-1 A-CSI-RS configuration(s) may be a subset ofone or more A-CSI-RS configurations that may be indicated from a commonDCI.

A WTRU that may receive one or more Type-1 A-CSI-RS configurations mayconsider other A-CSI-RS configurations in a common DCI that may not bein Type-1 A-CSI-RS configurations, such as Type-2 A-CSI-RSconfigurations. A WTRU that may not receive one or more Type-1 A-CSI-RSconfigurations may consider one or more A-CSI-RS configurations (e.g.,all A-CSI-RS configurations) in a common DCI to be Type-2 A-CSI-RSconfigurations.

A WTRU may receive an indication of a CSI-RS that may be used for A-CSIreporting between an A-CSI-RS and a P-CSI-RS when the WTRU may beinstructed (e.g., indicated) to report A-CSI in a subframe. Such anA-CSI-RS may be located in a same subframe that may include such areceived indication of a CSI-RS. Such a P-CSI-RS may be located in thesame subframe and/or one or more adjacent subframes.

One or more A-CSI-RS configurations may be indicated in a common DCIthat may be monitored in a common search space. One or more P-CSI-RSconfigurations may be configured via higher layer signaling, such as RRCsignaling.

A DCI that may be used to request A-CSI reporting may include a bitfield that may indicate one or more CSI-RS configurations that may beused for a measurement of A-CSI reporting between an A-CSI-RS and aP-CSI-RS.

One or more radio network temporary identifiers (RNTIs), each of whichmay be scrambled using one or more cyclic redundancy checks (CRCs) for aDCI, may be used for an A-CSI reporting request. Such an A-CSI reportingrequest may be used to indicate a CSI-RS configuration that may be usedfor measurement of A-CSI reporting between an A-CSI-RS and a P-CSI-RS. AWTRU may use a P-CSI-RS for A-CSI reporting where a cell-RNTI (C-RNTI)may be used. Such a WTRU may also, or instead, use an A-CSI-RS for A-CSIreporting where a C-RNTI+1 may be used.

A WTRU may receive a DL signal in a subframe that may contain one ormore A-CSI-RSs and/or one or more P-CSI-RSs. One or more of suchA-CSI-RSs and/or P-CSI-RSs may be used for RE muting of a downlinksignal. A WTRU may receive a PDSCH in a subframe that may contain one ormore A-CSI-RSs and/or one or more P-CSI-RSs. Such a WTRU may assume,consider, and/or determine that REs occupied by A-CSI-RSs and/orP-CSI-RSs are muted.

A WTRU may assume and/or determine that REs that may be occupied by,used by, and/or allocated to a CSI-RS (e.g., A-CSI-RS, P-CSI-RS) in aPDSCH resource may be muted REs of an associated PDSCH transmission.Such a WTRU may determine that muted REs of the associated PDSCHtransmission may be punctured REs and/or rate-matched REs, e.g., basedon one or more criteria that may be determined by such a WTRU.

Such criteria may include a type of an A-CSI-RS. For example, puncturingmay be used for a Type-1 A-CSI-RS and rate-matching may be used for aType-2 A-CSI-RS, or vice versa.

Such criteria may also, or instead, include a periodic or aperiodiccharacter of an RS. For example, rate-matching may be used for aP-CSI-RS and puncturing may be used for an A-CSI-RS, or vice versa.

Such criteria may also, or instead, include a modulation order that maybe used for a scheduled PDSCH. For example, puncturing may be used for alower modulation order (e.g., QPSK) while rate-matching may be used fora higher modulation order (e.g., 16QAM, 64QAM), or vice versa.

Such criteria may also, or instead, include a coding rate or aneffective coding rate that may be used for a scheduled PDSCH. Forexample, puncturing may be used for a coding rate or effective codingrate that may be below a threshold, while rate-matching may be used fora coding rate or effective coding rate that may be equal to or higherthan a threshold, or vice-versa. In an additional example, puncturingmay be used for a transport block size (TBS) that may be smaller than athreshold, while rate-matching may be used for a TBS that may be equalto or larger than a threshold, or vice-versa. Such thresholds may bepredefined and/or configured.

Such criteria may also, or instead, include a number of codewords and/ora rank. For example, puncturing may be used if a number of codewords isone (e.g., rank=1) and rate-matching may be used if a number ofcodewords is higher than one (e.g., rank>1), or vice-versa.

Such criteria may also, or instead, include an indication that may beincluded in a DCI. For example, a bit field may indicate whether a mutedRE of a scheduled PDSCH, where the RE may be muted due to a CSI-RS, maybe rate-matched around and/or punctured for demodulation.

RE muting may be used for one or more scheduled PDSCH REs that may havecollided with a CSI-RS. A use of RE muting may be determined based onone or more criteria that may be determined by a WTRU. Such criteria mayinclude a type of A-CSI-RS. For example, a WTRU may assume that REmuting may be used for a Type-1 A-CSI-RS and that no RE muting may beused for a Type-2 A-CSI-RS, or vice versa.

Such criteria may also, or instead, include a periodic or aperiodiccharacter of an RS. For example, a WTRU may determine that RE muting maybe used for a P-CSI-RS and that no RE muting may be used for anA-CSI-RS, or vice versa.

Such criteria may also, or instead, include a modulation order that maybe used for a scheduled PDSCH.

Such criteria may also, or instead, include a coding rate or effectivecoding rate that may be used for a scheduled PDSCH.

Such criteria may also, or instead, include a number of codewords and/ora rank.

Such criteria may also, or instead, include an indication that may beprovided in a DCI.

A WTRU may be configured to monitor an EPDCCH for one or more DCIs thatmay be associated with at least one of PDSCH scheduling, PUSCHscheduling, and/or common control information. The terms “enhancedPDCCH,” “EPDCCH,” “MTC PDCCH,” “MPDCCH,” “narrowband PDCCH,” and“NB-PDCCH” may be used interchangeably herein. “EPDCCH” may be referredto as a downlink control channel monitored, decoded, received, and/ortransmitted in a PDCCH region.

Where a WTRU may be configured to monitor an EPDCCH, one or more REsthat may be occupied by CSI-RS (e.g., A-CSI-RS, P-CSI-RS) in EPDCCHresources may be muted. EPDCCH REs that may collide with CSI-RS may bemuted.

A set of ECCE aggregation levels for EPDCCH candidates in an EPDCCHsearch space may be determined based on available REs (n_(EPDCCH)) in asubframe and/or a PRB-pair configured for an EPDCCH resource set. Suchavailable REs may exclude REs that may be used by a CSI-RS in thesubframe. Where a number of available REs may be greater than, orgreater than or equal to, a threshold (e.g., a predetermined threshold,a preconfigured threshold), a first set of ECCE aggregation levels maybe used and/or determined for an EPDCCH search space. A second set ofECCE aggregation levels may be used and/or determined for a EPDCCHsearch space where a number of available REs may be less than, or lessthan or equal to, a threshold (e.g., a predetermined threshold, apreconfigured threshold).

An RE that may be used for a CSI-RS may be determined to be an availableRE based on one or more of CSI-RS properties. One or more REs that maybe used for and/or occupied by a P-CSI-RS may be determined to beunavailable (e.g., muted). One or more REs that may be used for anA-CSI-RS may be determined to be available REs.

One or more REs that may be used for an A-CSI-RS may be determined to beavailable REs. A WTRU may consider such REs as muted REs in decoding oneor more EPDCCH candidates.

One or more REs that may be used for a P-CSI-RS may be determined to beunavailable REs. A WTRU may consider such REs as muted REs in decodingone or more EPDCCH candidates.

A set of one or more ECCE aggregation levels may be determined as afunction of a presence of a P-CSI-RS. Such a set of EPDCCH aggregationlevels may be determined independent of a presence of an A-CSI-RS.

A number of EREGs per ECCE may be determined based on a presence of anA-CSI-RS in a subframe. N₁ (e.g., 4) EREGs per ECCE may be used when,for example, an A-CSI-RS may not be presented in a subframe. N2 (e.g.,8) ERGEs per ECCE may be used when, for example, an A-CSI-RS may bepresented in a subframe.

A number of EREGs per ECCE may be determined based on a presence of anA-CSI-RS in a subframe and/or a number of REs that may be used for anA-CSI-RS in a PRB. Where a number of REs that may be used for anA-CSI-RS in a PRB may be less than, or less than or equal to, athreshold (e.g., a predetermined threshold, a preconfigured threshold)(e.g., N_(THRESHOLD)=16), N₁ EREGs per ECCE may be used. Where a numberof REs that may be used for an A-CSI-RS in a PRB may be greater than, orgreater than or equal to, a threshold (e.g., a predetermined threshold,a preconfigured threshold), N2 EREGs per ECCE may be used.

A number of REs that may be used for an A-CSI-RS may include a count ofREs used for one or more Type-1 A-CSI-RSs or Type-2 A-CSI-RSs (e.g.,used only for one or more Type-1 A-CSI-RSs or Type-2 A-CSI-RSs). Athreshold (e.g., a predetermined threshold, a preconfigured threshold)may be based on a number of PRB-pairs that may be configured for anEPDCCH resource set. N₁ values may differ from N2 values based on atleast one of a subframe type, a CP length, and/or a duplex mode (e.g.,TDD or FDD).

EPDCCH RE muting may be used for REs that may be occupied by a CSI-RS.Puncturing and/or rate-matching for such muted REs may be determinedbased on a type of an A-CSI-RS. For example, EPDCCH RE puncturing may beused for a Type-1 A-CSI-RS, while EPDCCH RE rate-matching may be usedfor a Type-2 A-CSI-RS, or vice versa.

Puncturing and/or rate-matching for such muted REs may also, or instead,be determined based on a periodic or aperiodic character of an RS. Forexample, EPDCCH RE rate-matching may be used for a P-CSI-RS, whileEPDCCH RE puncturing may be used for an A-CSI-RS, or vice versa.

Puncturing and/or rate-matching for such muted REs may also, or instead,be determined based on an EPDCCH search space type. For example, EPDCCHRE puncturing may be used for an A-CSI-RS in EPDCCH common search space,while EPDCCH RE rate-matching may be used for an A-CSI-RS in EPDCCHWTRU-specific search space, or vice versa.

Puncturing and/or rate-matching for such muted REs may also, or instead,be determined based on an ECCE aggregation level of an EPDCCH candidate.

A use of EPDCCH RE muting for EPDCCH REs that may be occupied by aCSI-RS may be determined based on a type of an A-CSI-RS. EPDCCH REmuting for EPDCCH REs that may be occupied by a CSI-RS may be used for atype-1 A-CSI-RS, while no EPDCCH RE muting may be used for a Type-2A-CSI-RS, or vice versa. Alternatively, or in addition, EPDCCH RE mutingfor EPDCCH REs that may be occupied by a CSI-RS may be used based on aperiodic or aperiodic character of an RS. For example, EPDCCH RE mutingmay be used for a P-CSI-RS, while no EPDCCH RE muting may be used for anA-CSI-RS, or vice versa. Alternatively, or in addition, EPDCCH RE mutingfor EPDCCH REs that may be occupied by a CSI-RS may be used based on anEPDCCH search space type. For example, EPDCCH RE muting may be used fora CSI-RS that may be in an EPDCCH common search space, while no EPDCCHRE muting may be used for a CSI-RS that may be in an EPDCCHWTRU-specific search space, or vice versa. Alternatively, or inaddition, EPDCCH RE muting for EPDCCH REs that may be occupied by aCSI-RS may be used based on an ECCE aggregation level of an EPDCCHcandidate.

EPDCCH REs that may be used for an A-CSI-RS may be consideredunavailable REs (e.g., muted REs). An A-CSI-RS and/or A-CSI-RS patternsfor EPDCCH RE muting may be indicated in a DCI that may be transmittedand/or monitored in a PDCCH common search space. A WTRU may determine anEPDCCH aggregation level set for an EPDCCH WTRU-specific search space ina subframe based on a presence or absence of, and/or patterns of, anA-CSI-RS that may be indicated in a DCI that may be received and/ormonitored in a PDCCH common search space in a same subframe.

A DCI may be transmitted and/or received in a subframe (e.g., only inthe subframe) in which one or more A-CSI-RSs may be presented.Alternatively, or in addition, a DCI may be transmitted and/or receivedin all subframes irrespective of a presence of an A-CSI-RS. A bit fieldmay be used to indicate an absence or presence of an A-CSI-RS and/or oneor more A-CSI-RS patterns. Where such a bit field may indicate anabsence of an A-CSI-RS in a subframe, a WTRU may determine that there isno A-CSI-RS in the subframe. Alternatively, or in addition, an EPDCCHaggregation level set determination may be based on available REs, whereavailable REs may be determined based on an absence or presence of anA-CSI-RS. Where a WTRU fails to receive a DCI that may indicate anabsence or presence of an A-CSI-RS in a subframe, the WTRU may notmonitor EPDCCH in the subframe.

A collision between an EPDCCH and an A-CSI-RS may be avoided using oneor more A-CSI-RS presences and/or transmissions. Such A-CSI-RS presencesand/or transmissions may be limited to a subset of time and/or frequencyresources. Subframes and/or radio frames may have a DCI that mayindicate a presence of an A-CSI-RS. A WTRU may monitor the DCI of suchsubframes and/or radio frames. Such subframes and/or radio frames may belimited to a subset of subframes and/or radio frames in a system. Such asubset of subframes and/or radio frames may be configured via higherlayer signaling.

Alternatively, or in addition, subframes and/or radio frames that mayhave a DCI that may be monitored by a WTRU may indicate a presence of anA-CSI-RS. Such subframes and/or radio frames that may be monitored bysuch a WTRU may be determined as a function of one or more of a subframenumber, a radio frame number (e.g., a system frame number (SFN)), aphysical cell-ID, and/or a WTRU-ID.

Alternatively, or in addition, a WTRU may determine that an A-CSI-RS maynot be transmitted and/or located in one or more PRBs configured and/orused for an EPDCCH, for example, regardless of whether one or moreA-CSI-RSs may or may not be presented in a subframe.

A WTRU-specific search space may be switched between a PDCCH and anEPDCCH based on a presence of an A-CSI-RS in a subframe. For example, aWTRU may be configured with an EPDCCH for a WTRU-specific search spaceand, where the WTRU may receive an indication of a presence of anA-CSI-RS in a subframe, the WTRU may monitor a PDCCH for theWTRU-specific search space in the subframe. A PDCCH WTRU-specific searchspace may be used as a fallback WTRU-specific search space. Such afallback WTRU-specific search space may be used where one or moreA-CSI-RSs may collide with an EPDCCH WTRU-specific search space.Alternatively, or in addition, a presence of an A-CSI-RS in a subframemay be indicated by a DCI. Such a DCI may be transmitted and/ormonitored in a PDCCH common search space. Alternatively, or in addition,a presence of an A-CSI-RS in a subframe may be indicated in a previoussubframe. Alternatively, or in addition, a WTRU may not monitor one ormore EPDCCH candidates in a subframe where such one or more EPDCCHcandidates may collide with one or more A-CSI-RSs that may be present inthe subframe.

A set of antenna ports for a CSI-RS configuration may be indicated in atransmission of a subset of PRBs. For example, a set of antenna ports(e.g., a present set of antenna ports) for a CSI-RS configuration in aPRB may be determined based on a PRB index. Alternatively, or inaddition, a set of antenna ports (e.g., a present set of antenna ports)for a first CSI-RS configuration may be presented in one or more PRBsthat may have or be associated with even-numbered PRB indexes, while aset of antenna ports (e.g., a present set of antenna ports) for a secondCSI-RS configuration may be presented in one or more PRBs that may haveor be associated with odd-numbered PRB indexes, or vice versa.

A WTRU may receive an indication of a subset of one or more PRBs thatmay contain an associated CSI-RS. For example, a first set of PRBs(e.g., a set that may have even-numbered PRB indexes) may be indicatedfor a first WTRU, while a second set of PRBs (e.g., a set that may haveodd-numbered PRB indexes) may be indicated for a second, different WTRU.Such an indication may be signaled as a part of one or more CSI-RSconfiguration parameters. Alternatively, or in addition, such anindication may be signaled in an associated DCI for A-CSI-RS triggering.

CSI-RS PRB-level nulling may be used, where a set of antenna ports for aCSI-RS configuration may be transmitted in a subset of one or more PRBs.Use of such nulling may be determined based on a number of antennaports. For example, where a number of antenna ports for a CSI-RS may begreater than, or greater than or equal to, a threshold (e.g., apredetermined threshold, a preconfigured threshold) (e.g., 16), CSI-RSPRB-level nulling may be used. A set of antenna ports for a CSI-RSconfiguration may be used interchangeably with a number of antennaports.

PRB indices for which CSI-RS PRB-level nulling may be used may bedetermined based on a subframe and/or a radio frame number.Alternatively, or in addition, PRB indices for which CSI-RS PRB-levelnulling may be used may be determined based on a CSI-RS PRB-levelnulling may be determined based on a WTRU-ID (e.g., C-RNTI).Alternatively, or in addition, PRB indices for which CSI-RS PRB-levelnulling may be used may be determined based on a P-CSI-RS and/or anA-CSI-RS.

A set of one or more PRBs associated with a CSI-RS transmission may bedetermined based on one or more of a number of antenna ports configuredfor the CSI-RS, one or more types of CSI-RSs (e.g., P-CSI-RS, A-CSI-RS),one or more system parameters (e.g., subframe number, radio framenumber, physical cell-ID), and/or one or more WTRU-specific parameters(e.g., WTRU-ID). Such a determined set of PRBs may include all PRBs in asubframe or a subset of PRBs in a subframe.

One or more downlink control signals may be used for an A-CSI-RS. Forexample, two control signal indications (e.g., DCIs) may be used for anA-CSI-RS. A first DCI may be used to indicate one or more activeA-CSI-RS patterns (e.g., an active A-CSI-RS set). A second DCI may beused to indicate active A-CSI-RS patterns that may be used for CSImeasurement. An active A-CSI-RS set may include one or more A-CSI-RSconfigurations that may be active and/or presented in an associated timewindow and/or location (e.g., a subframe). An active A-CSI-RS set may beinterchangeably used as a common A-CSI-RS set.

An active A-CSI-RS set may be a subset of A-CSI-RS patterns that may beconfigured by higher layer signaling. Alternatively, or in addition, aWTRU may determine that one or more A-CSI-RS patterns in an activeA-CSI-RS set may be presented in an associated time location (e.g., asubframe). Alternatively, or in addition, a WTRU may monitor, receive,and/or attempt to decode a first DCI that may carry one or more activeA-CSI-RS patterns. This may be performed regardless of whether such aWTRU may be configured for A-CSI-RS based A-CSI reporting.Alternatively, or in addition, a WTRU may use active A-CSI-RS setinformation where such a WTRU may receive, attempt to decode, and/or bescheduled for a downlink transmission (e.g., PDSCH, EPDCCH) in anassociated time window and/or location (e.g., a PDSCH region in asubframe). Alternatively, or in addition, RE muting may be used for adownlink transmission (e.g., PDSCH, EPDCCH) on REs used and/or occupiedby an active A-CSI-RS set in a subframe. Alternatively, or in addition,an associated time window for one or more active A-CSI-RS patterns maybe determined based on activation and/or deactivation of the activeA-CSI-RS patterns. For example, active A-CSI-RS patterns may beactivated in a subframe n and deactivated in another subframe n+k.

One or more A-CSI-RS patterns in an active A-CSI-RS set may be indicatedin a DCI (e.g., such as a second DCI as described herein that may beused to indicate active A-CSI-RS patterns to use for CSI measurement)and referred to as a dedicated A-CSI-RS set. The terms “dedicatedA-CSI-RS set” and “measurement A-CSI-RS set” may be used interchangeablyherein.

A dedicated A-CSI-RS set may be one or more WTRU-specific A-CSI-RSpatterns that may be used for CSI measurement. Alternatively, or inaddition, a dedicated A-CSI-RS set may be used for CSI reporting.Alternatively, or in addition, partial configuration information (e.g.,transmission power, quasi-collocation, a number of antenna ports) of adedicated A-CSI-RS set may be configured by higher layer signaling,while some or all remaining configuration information (e.g., a CSI-RSreuse pattern) may be indicated in another DCI (e.g., a second DCI).

A DCI for an active A-CSI-RS set information (e.g., a first DCI) may betransmitted and/or monitored in a common search space (CSS), such as aPDCCH CSS and/or an EPDCCH CSS. Such a DCI may be monitored by a WTRU inPDCCH CSS and/or an EPDCCH CSS, where the PDCCH CSS and/or an EPDCCH CSSfor the DCI may be different from a PDCCH CSS and/or an EPDCCH CSS forother DCIs. Such other DCIs may be carrying multi-cast and/or broadcastsignals. For example, control channel elements, such as a CCE and/orECCE, which may be referred to herein as (E)CCE, #0˜#15 may be used fora PDCCH CSS and/or an EPDCCH CSS for such other DCIs that may becarrying multi-cast and/or broadcast signals (e.g., DCIs with P-RNTI,SI-RNTI). Control channel elements (E)CCE #16˜#32 may be used for aPDCCH CSS and/or an EPDCCH CSS for such a DCI. The DCI may include theactive A-CSI-RS set.

Such a DCI (e.g., the first DCI) may be scrambled with a common RNTI.Alternatively, or in addition, such a DCI may include a bit field thatmay indicate an active A-CSI-RS set. Such a bit field may be a bitmapthat may be associated with one or more N_(A-CSI-RS) A-CSI-RSconfigurations. For example, where one or more N_(A-CSI-RS) A-CSI-RSconfigurations may be used and/or configured via higher layer signaling,N_(A-CSI-RS) bits may be used for the bit field and/or may indicateactive and/or non-active A-CSI-RS configurations. Alternatively, or inaddition, one or more groups of one or more active A-CSI-RS sets may bedefined, predefined, and/or configured. Such one or more groups may beindicated in such a DCI (e.g., the first DCI).

A different DCI (e.g., a second DCI, as opposed to a first DCI describedabove) may be associated with dedicated A-CSI-RS set information thatmay be transmitted and/or monitored in a WTRU-specific search space.Such a different DCI (e.g., the second DCI) may be used for an uplinkgrant (e.g., DCI format 0/4) where a bit field may be used to indicate adedicated A-CSI-RS set that may be used in an uplink grant.Alternatively, or in addition, a flag bit may be included and/or used insuch a DCI (e.g., the second DCI) to indicate whether a bit fieldassociated with dedicated A-CSI-RS set information may be included inthe DCI. Where a flag bit may be set to TRUE, a WTRU may use one or moreA-CSI-RSs indicated by the dedicated A-CSI-RS set information for A-CSIreporting. Where a flag bit may be set to FALSE, a WTRU may use aP-CSI-RS for A-CSI reporting, where such a P-CSI-RS may be located in asame subframe or in an adjacent subframe.

One or more A-CSI-RS patterns in an active A-CSI-RS set that may not beindicated in a dedicated A-CSI-RS set may be considered to be Type-2A-CSI-RSs, while A-CSI-RS patterns that may be indicated in the activeA-CSI-RS set may be considered to be Type-1 A-CSI-RSs.

An active A-CSI-RS set may be configured via a higher layer signaling(e.g., RRC, broadcasting). A dedicated A-CSI-RS set may be indicated ina DCI. One or more A-CSI-RS patterns may be configured as an activeA-CSI-RS set via higher layer signaling, while one or more A-CSI-RSpatterns within the active A-CSI-RS set may be indicated in a DCI as adedicated A-CSI-RS set.

An active A-CSI-RS set may be configured by a higher layer signaling andmay be used for RE muting of a downlink transmission (e.g., PDSCH,EPDCCH, PBCH, PMCH) in a subframe where a WTRU receives one or more ofan A-CSI reporting request indication, a dedicated A-CSI-RS setindication, and/or an indication in a DCI. Such an indication in a DCImay be used for RE muting of a downlink transmission for REs that may beused for an active A-CSI-RS. Such an indication may be transmitted in aDCI that may be associated with PDSCH scheduling.

RE muting of a downlink transmission for one or more REs that may beused for one or more active A-CSI-RS sets may be used at one or moretimes (e.g., one or more predetermined times, one or more preconfiguredtimes) and/or at one or more frequency locations (e.g., one or morepredetermined frequency locations, one or more preconfigured frequencylocations). Such times and/or frequency locations may be a subset ofsubframes that may be configured by higher layer signaling.Alternatively, or in addition, such times and/or frequency locations maybe determined as a function of at least one of a subframe number, aphysical cell-ID, a radio frame number (e.g., SFN), and/or a WTRU-ID(e.g., C-RNTI).

A DCI (e.g., a first DCI that may or may not be a same first DCI asdescribed elsewhere herein) may carry active A-CSI-RS set information.Another DCI (e.g., a second DCI that may or may not be a same second DCIas described elsewhere herein) may carry dedicated A-CSI-RS setinformation. A WTRU may receive, attempt to decode, and/or monitor sucha DCI carrying active A-CSI-RS set information (e.g., the first DCI) andsuch a DCI carrying dedicated A-CSI-RS set information (e.g., the secondDCI) to obtain one or more Type-1 A-CSI-RS configurations and/or one ormore Type-2 A-CSI-RS configurations. For example, a dedicated A-CSI-RSset may be considered a Type-1 A-CSI-RS configuration, while one or moreremaining other A-CSI-RSs in the active A-CSI-RS set (that may be notindicated in the dedicated A-CSI-RS set) may be considered Type-2A-CSI-RSs.

One or more fallback A-CSI-RS set configurations may be determinedand/or used. One or more such fallback A-CSI-RS sets may be one or moresets of A-CSI-RS configurations that may be used for RE muting of adownlink transmission. One or more such fallback A-CSI-RS sets may bethe same as one or more sets of A-CSI-RS patterns that may be configuredvia higher layer signaling. A WTRU may use such one or more fallbackA-CSI-RS sets for RE muting of a downlink transmission where such a WTRUmay fail to receive a DCI (e.g., the first DCI) (e.g., that may includeactive A-CSI-RS set information). For example, such a WTRU may havereceived another DCI (e.g., the second DCI) (e.g., that may includededicated A-CSI-RS set information) in a subframe and may use one ormore fallback A-CSI-RS sets for RE muting of a downlink transmission.

A WTRU may determine to not receive a downlink signal in a subframewhere such a WTRU fails to receive a DCI (e.g., the first DCI) (e.g.,that may include active A-CSI-RS set information). For example, such aWTRU may have received another DCI (e.g., the second DCI) that, forexample, may include a dedicated A-CSI-RS set. Such a WTRU may alsoreceive yet another DCI for PDSCH scheduling in a same subframe, whilehaving missed the DCI (e.g., the first DCI) that may have includedactive A-CSI-RS set information. Such a WTRU may determine to not decodePDSCH and/or may measure A-CSI from the dedicated A-CSI-RS set (e.g., asreceived in the second DCI). Such a WTRU may not buffer PDSCH for ahybrid automatic repeat request (HARQ) operation (e.g., because the softbuffer may be corrupted). Alternatively, or in addition, such a WTRU maytransmit a discontinuous transmission (DTX) for a corresponding PDSCHthat, for example, may not be decoded based on the WTRU missing the DCI(e.g., the first DCI) that may have included active A-CSI-RS setinformation.

A WTRU may receive an indication that may instruct or otherwise causethe WTRU to report A-CSI in a subframe n. An A-CSI-RS for the A-CSImeasurement may be reported in a subframe m. Such a WTRU may reportrequested A-CSI in a subframe n+k via an uplink channel.

An A-CSI reporting time (e.g., n+k) may be determined based on one ormore associated CSI-RS properties. A presence of an A-CSI-RS for A-CSIreporting may not be known until a WTRU may receive an indication of anA-CSI-RS presence. This may result in increased processing time toperform channel measurement from an A-CSI-RS. k=4 may be used whereA-CSI reporting may be associated with a P-CSI-RS. k>4 may be used whereA-CSI reporting may be associated with an A-CSI-RS.

A-CSI reporting timing (e.g., n+k) may be determined based on one ormore associated CSI-RS properties. Such reporting timing (e.g., n+k) maybe determined as a function of one or more associated CSI-RS types for atriggered A-CSI. Where an associated CSI-RS type may be A-CSI-RS,reporting timing may be determined based on a time location of anA-CSI-RS m. Where m may be the same as n, reporting timing n+k may bethe same for both P-CSI-RS and A-CSI-RS. Where a time location ofA-CSI-RS may be m=n+t, reporting timing may be determined as n+t+k.

A-CSI reporting timing may be determined based on an associated A-CSI-RSconfiguration. For example, such reporting timing may be determinedbased on an A-CSI-RS configuration index. As shown in exemplary A-CSI-RSconfigurations (or reuse patterns) 500 for 8Tx illustrated in FIG. 5 ,five A-CSI-RS configurations (e.g., configurations 501, 502, 503, 504,505 shown in FIG. 5 ) may be used. A time location of an A-CSI-RSconfiguration may be used to determine a reporting time. n+k may be usedas reporting timing where, for example, an A-CSI-RS configuration, suchas exemplary A-CSI-RS Config. 501 shown in FIG. 5 , may be indicated asan associated A-CSI-RS for A-CSI reporting. Alternatively, or inaddition, n+k+1 may be used as reporting timing where, for example,associated A-CSI-RS configurations, such as exemplary A-CSI-RS Config.502, A-CSI-RS Config. 503, and/or A-CSI-RS Config. 501 of FIG. 5 , maybe indicated as an associated A-CSI-RS for A-CSI reporting.Alternatively, or in addition, n+k+2 may be used as reporting timingwhere, for example, an associated A-CSI-RS configuration, such asexemplary A-CSI-RS Config. 505 of FIG. 5 , may be indicated as anassociated A-CSI-RS for A-CSI reporting.

A reporting time (e.g., n+k) for A-CSI may be used irrespective ofassociated CSI-RS properties. A CSI measurement search space may berestricted based on such associated CSI-RS properties for A-CSIreporting. A CSI measurement search space may include and/or indicateone or more CSI types that may be reported, a range of each of one ormore CSI types, a parameter of each of one or more CSI types, and/or avalue of each of one or more CSI types. One or more subsets of, or allof, such values and/or indicators may be associated with one another.More than one of multiple CSI types to report, multiple ranges of CSItypes, multiple parameters of CSI types, and multiple values of CSItypes may be included and/or indicated in a CSI measurement searchspace.

CSI types may include one or more of a wideband CQI, a subband CQI, anRI, a wideband PMI, a subband PMI, a precoding type indication (PTI), aCSI-RS Resource Indication (CRI), and/or a subband index. A range of aCSI type that may be related to CQI (e.g., wideband CQI, subband CQI)may be predefined or predetermined as a signal-to-noise ratio (SNR)range (e.g., a range from 0 to 15), where such an SNR range may bedefined as/at a modulation and coding scheme (MCS) level. A range of aCSI type that may be related to PMI and/or RI (e.g., wideband CQI,subband CQI) may be determined based on a number of antenna ports thatmay be configured and/or a transmission mode and/or transmission schemethat may be configured. A parameter of a CSI type that may be related tosubband reporting (e.g., subband CQI, subband PMI) may include a subbandsize for such reporting.

A CSI measurement search space may be restricted where an associatedCSI-RS may be an A-CSI-RS. For example, RI may be restricted to a subsetof candidates. Such an RI may be searched within full candidates of {1,2, 3, 4} where A-CSI may be triggered based on a P-CSI-RS while RI maybe searched within restricted candidates of {1, 2} where A-CSI may betriggered based on an A-CSI-RS. Restricted candidates of an RI may bedetermined based on an RI reporting value, such as a most recent RIreporting value. Restricted candidates of an RI may be configured viahigher layer signaling. Restricted candidates of an RI may be indicatedin an associated DCI that may trigger A-CSI reporting. For example, suchrestricted candidates of an RI may be a single candidate (e.g., {2}). Amaximum RI value may be determined based on one or more CSI-RS types(e.g., P-CSI-RS, A-CSI-RS).

A number of CSI process may be limited. For example, Nc CSI processesmay be configured via higher layer signaling. An eNodeB may triggerA-CSI reporting for such Nc CSI processes where one or more P-CSI-RSsmay be used. A subset of Nc CSI processes may be used for A-CSIreporting when one or more A-CSI-RSs may be used. A single CSI processmay be used (e.g., only used) for A-CSI reporting where A-CSI may bemeasured from an A-CSI-RS. A CSI process index for A-CSI reporting maybe indicated in an associated DCI that may be used for A-CSI reporting.

PMI may be limited to a subset of candidates. For example, PMIcandidates for A-CSI reporting with P-CSI-RS may be determined based ona codebook subset restriction that may be configured via higher layersignaling. PMI candidates for A-CSI reporting with an A-CSI-RS may bebased on a subset of PMI candidates that may be determined for A-CSIreporting with a P-CSI-RS. For example, a two-stage codebook subsetrestriction may be used for A-CSI reporting with an A-CSI-RS. A firstcodebook subset restriction may be used for both a P-CSI-RS and anA-CSI-RS while a second codebook subset restriction may be used for anA-CSI-RS.

Where PMI may be limited to a subset of candidates, a first codebooksubset restriction may be a superset of a second codebook subsetrestriction. Alternatively, or in addition, a first codebook subsetrestriction may be configured via higher layer signaling. Alternatively,or in addition, a second codebook subset restriction may be configuredvia higher layer signaling (e.g., separate signaling from that used tosignal the first codebook subset restriction) that may be used for WTRUsthat may be configured with an A-CSI-RS. Alternatively, or in addition,a second codebook subset restriction may be indicated dynamically froman associated DCI that may trigger A-CSI reporting with an A-CSI-RS.

PMI may be indicated in an associated DCI that may trigger A-CSIreporting with an A-CSI-RS. For example, a specific PMI may be indicatedfor use with A-CSI reporting. A WTRU may use the indicated specific PMIto search other CSI reporting indices (e.g., CQI, RI).

A subband size of subband CQI and/or a subband PMI reporting may bedetermined based on one or more CSI-RS types (e.g., P-CSI-RS, A-CSI-RS).For example, a first subband size may be used for subband CQI and/orsubband PMI reporting where CSI reporting may be based on a P-CSI-RS. Insuch an example, a second subband size may be used for subband CQIand/or subband PMI reporting where CSI reporting may be based on anA-CSI-RS. Such a first subband size may be narrower than a secondsubband size, or vice versa. Such a second subband size may be multiplesof such a first subband size. Alternatively, or in addition, such asecond subband size may be indicated in a DCI that may trigger A-CSIreporting with an A-CSI-RS.

One or more subbands that may be used for CSI reporting may be limitedwhere A-CSI reporting may be triggered based on an A-CSI-RS. Forexample, Ns subbands may be used for A-CSI reporting where a P-CSI-RSmay be used for CSI measurement while Na subbands may be used for A-CSIreporting where an A-CSI-RS may be used for CSI measurement. Na may besmaller than Ns. Ns may be determined based on a system bandwidth. Namay be configured via higher layer signaling and/or predetermined. Nsmay be indicated in a DCI that may trigger A-CSI reporting with anA-CSI-RS. A subband (e.g., a specific subband) may be indicated in a DCIthat may trigger A-CSI reporting with an A-CSI-RS.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom-access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

What is claimed is:
 1. A wireless transmit/receive unit (WTRU) forreceiving a physical downlink shared channel (PDSCH) transmission, theWTRU comprising: a processor, wherein the processor is configured to:receive configuration information for a channel state informationreference signal (CSI-RS), wherein the configuration informationindicates one or more CSI-RS resources; receive scheduling informationfor reception of the PDSCH transmission, wherein the schedulinginformation indicates PDSCH resources, wherein the PDSCH resourcesinclude a first number of resources and a second number of resources,and wherein the first number of resources overlaps with at least aCSI-RS resource from the one or more CSI-RS resources; and receive thePDSCH transmission using the first number of resources and the secondnumber of resources when the CSI-RS is an aperiodic non-zero powerCSI-RS (NZP-CSI-RS).
 2. The WTRU of claim 1, wherein the processor isconfigured to receive the PDSCH transmission using the first number ofresources and the second number of resources when the CSI-RS is theaperiodic NZP-CSI-RS by receiving the PDSCH transmission using at leasta PDSCH modulation symbol, wherein the PDSCH modulation symbol maps to aPDSCH resource from the PDSCH resources.
 3. The WTRU of claim 1, whereinthe processor is further configured to receive the PDSCH transmissionusing the second number of resources when the CSI-RS is a periodiczero-power CSI-RS (ZP-CSI-RS), a periodic NZP-CSI-RS, or an aperiodicZP-CSI-RS.
 4. The WTRU of claim 3, wherein receiving the PDSCHtransmission using the second number of resources when the CSI-RS is theperiodic ZP-CSI-RS, the periodic NZP-CSI-RS, or the aperiodic ZP-CSI-RS,comprises receiving the PDSCH transmission using at least a PDSCHmodulation symbol, wherein the PDSCH modulation symbol maps to a PDSCHresource from the second number of resources.
 5. The WTRU of claim 1,wherein the PDSCH resources comprises a resource element.
 6. The WTRU ofclaim 1, wherein the CSI-RS resource comprises a resource element.
 7. Amethod performed by a wireless transmit/receive unit (WTRU) forreceiving a physical downlink shared channel (PDSCH) transmission, themethod comprising: receiving configuration information for a channelstate information reference signal (CSI-RS), wherein the configurationinformation indicates one or more CSI-RS resources; receiving schedulinginformation for reception of the PDSCH transmission, wherein thescheduling information indicates PDSCH resources, wherein the PDSCHresources include a first number of resources and a second number ofresources, and wherein the first number of resources overlaps with atleast a CSI-RS resource from the one or more CSI-RS resources; andreceiving the PDSCH transmission using the first number of resources andthe second number of resources when the CSI-RS is an aperiodic non-zeropower CSI-RS (NZP-CSI-RS).
 8. The method of claim 7, wherein receivingthe PDSCH transmission using the first number of resources and thesecond number of resources when the CSI-RS is the aperiodic NZP-CSI-RScomprises receiving the PDSCH transmission using at least a PDSCHmodulation symbol, wherein the PDSCH modulation symbol maps to a PDSCHresource from the PDSCH resources.
 9. The method of claim 7, wherein themethod further comprises receiving the PDSCH transmission using thesecond number of resources when the CSI-RS is a periodic zero-powerCSI-RS (ZP-CSI-RS), a periodic NZP-CSI-RS, or an aperiodic ZP-CSI-RS.10. The method of claim 9, wherein receiving the PDSCH transmissionusing the second number of resources when the CSI-RS is the periodicZP-CSI-RS, the periodic NZP-CSI-RS, or the aperiodic ZP-CSI-RS,comprises receiving the PDSCH transmission using at least a PDSCHmodulation symbol, wherein the PDSCH modulation symbol maps to a PDSCHresource from the second number of resources.
 11. The method of claim 7,wherein the PDSCH resources comprises a resource element.
 12. The methodof claim 7, wherein the CSI-RS resource comprises a resource element.13. The method of claim 7, wherein the method further comprises sendingan indication of a channel measurement to a network node, wherein thechannel measurement is associated with the CSI-RS.
 14. A wirelesstransmit/receive unit (WTRU) for receiving a physical downlink sharedchannel (PDSCH) transmission, the WTRU comprising: a processor, whereinthe processor is configured to: receive configuration information for achannel state information reference signal (CSI-RS), wherein theconfiguration information indicates one or more CSI-RS resources;receive scheduling information for reception of the PDSCH transmission,wherein the scheduling information indicates PDSCH resources, whereinthe PDSCH resources include a first number of resources and a secondnumber of resources, and wherein the first number of resources overlapswith at least a CSI-RS resource from the one or more CSI-RS resourcesreceive the PDSCH transmission using the first number of resources andthe second number of resources when the CSI-RS is an aperiodic non-zeropower CSI-RS (NZP-CSI-RS); and send an indication of a channelmeasurement to a network node, wherein the channel measurement isassociated with the CSI-RS.
 15. The WTRU of claim 14, wherein theprocessor is configured to receive the PDSCH transmission using thefirst number of resources and the second number of resources when theCSI-RS is the aperiodic NZP-CSI-RS by receiving the PDSCH transmissionusing at least a PDSCH modulation symbol, wherein the PDSCH modulationsymbol maps to a PDSCH resource from the PDSCH resources.
 16. The WTRUof claim 14, wherein the processor is further configured to receive thePDSCH transmission using the second number of resources when the CSI-RSis a periodic zero-power CSI-RS (ZP-CSI-RS), a periodic NZP-CSI-RS, oran aperiodic ZP-CSI-RS.
 17. The WTRU of claim 16, wherein receiving thePDSCH transmission using the second number of resources when the CSI-RSis the periodic ZP-CSI-RS, the periodic NZP-CSI-RS, or the aperiodicZP-CSI-RS, comprises receiving the PDSCH transmission using at least aPDSCH modulation symbol, wherein the PDSCH modulation symbol maps to aPDSCH resource from the second number of resources.
 18. The WTRU ofclaim 14, wherein the PDSCH resources comprises a resource element. 19.The WTRU of claim 14, wherein the CSI-RS resource comprises a resourceelement.